GPatrick - thank you for this info.  I do have the instructions you sent and have taken the dimensions that you indicate. 
I should have included how to remove/install the collar that is mounted near the distributor housing, any assistance is appreciated.

I’m changing my MSD distributor to lock out the advance mechanism, so the MSD EFI can control the timing.  I need to move the collar about ½” to lift the shaft, turn the shaft and reset it into a hole that locks out the advance mechanism, and reset the collar.  
When I pulled the distributor, the drive gear was worn on 11 of the 15 teeth on the gear.  I’m following up with Comp Cams on that issue, but need to replace the gear regardless.
 

May be I am "just-living-right" butt if I rememberize correctly I just put the distrib. in my vise...used a small center punch and knocked the pin out...tapped the old gear off with a hammer...slipped the melonized gear on and re-drilled the hole 90* over.
End of project. Happened many-moons ago... Zero issues...
Made a bushing to slip on the post in the distrib to limit total advance.
Only issue I had was removing that ugly lil retaining spring clip in the top of the shaft. I left it out when reassembling the distrib.
Works flaw-Leslie !
6sal6

Bob - The gear I removed is a steel gear for roller cams.  The engine that the EFI system is going into has a flat tappet cam so I swapped to iron.  If it turns out that you need a steel gear, this one has never been run and for the cost of shipping I'll make you a deal you can't refuse.

My method, as usual, is different than most. I use a cutoff wheel to cut the gear off the shaft because I tried a puller once and managed to bell the end of the shaft. Carefully cutting the gear away gets it off with zero damage.
To install the new gear, first I wrapped the shaft with masking tape to mark where the new gear needs to stop during installation.  I put the distributor in the freezer and used a propane torch to heat the gear. With the shaft pointing up, held in a vise, the heated gear will easily slide onto the shaft.
I would say the chances of you getting the hole in the gear to line up with the existing gear are close to zero.  I think most are hand drilled and that makes every one different.  The new gear should be drilled halfway through, and rotate it so the new hole is 90° from the old shaft hole.  The tape will stop the gear’s travel on the shaft.  Let it air cool and it will lock in place. Then complete the hole drilling through the shaft and gear. Install the roll pin.
I do not like the fact that there are two possibly intersecting holes in the shaft, but most rebuilt distributors are done this way, so it apparently does not cause problems.
Be advised there are gears with slightly varying ID’s. If your fits loose on the shaft, rest assured it will fail quickly.

I thought small block Ford gears have 14 teeth.  Regardless, are all of the bad teeth together or is there spacing between some of the wear.  If they are grouped together I would be concerned with radial runout of the distributor shaft (possible), distributor gear runout (less likely), bad heat treat on the distributor gear (possible) or a poorly machined cam gear (possible).  Depending on how much of the MSD gear assembly lube you had on the distributor gear and if it was uniformly placed around the gear the gear could have been damaged in the first few moments of operation.

What is the part number of your distributor?  

There should not be any indication of localized wear on the distributor shaft.  To me, this points to radial runout of the cam gear forcing the distributor shaft radially as it rotates.  This is not something you could see looking down the distributor hole - it could be a pattern machined into the cam.  I'm also not convinced that the MSD cast gear is correct but perhaps with a good break-in it will survive.  I would pull the distributor at 500 miles and inspect the gear.  If it shows wear one one side again, the cam becomes even more suspect.  There is a chance that the distributor shaft is bent.  I'm not sure there is a good way to check radial runout but you may be able to apply a slight side load to take out any bearing play and slowly rotate while checking with a dial indicator.  

I am running after market roller cams in my 347 SBF and my 447 FE and I am using the MSD steel gears on both.  To date I am not experiencing any wear on either setup.  MSD doesn't help with the gear selection because they typically indicate that both the steel and iron gears are melonized.

Cam gears are always a 'head-scratcher' for me. I was under the impression a STEEL gear was REQUIRED for a roller cam
Butt..a FT cam would survive with EITHER type (steel or cast arn)....Then the cam folks and others throw out the old
"melonize" word...!
6sally6

After considerable research, and talking to various cam manufacturers and distributor manufacturers tech departments over the years, this is what I've come to know about cam and distributor gear compatibility:

There are 4 main types of camshaft material: cast iron, selectively austempered ductile iron (SADI), 5150 billet steel, and 8620 billet steel.  If you have an aftermarket cam I would advise finding out from which material the cam is made, because with distributor gear material requirement for each one can be different.    

I believe all OEM flat tappet cams are cast iron.  This was the standard for decades.   You should run a cast gear with a cast cam.  However, every source I've read says you can also run a melonized gear on a cast iron cam (more on this in a minute).

SADI seems to be the core material used for a lot of aftermarket roller cams.  Basically the lobes are hardened, but the core is relatively soft.  This was done to keep costs down.  If your roller cam has shiny lobes but the areas between the lobes isn't; its SADI.  These cams need a steel or melonized distributor gear, unless it has a pressed on iron gear, in which case you would use a cast iron or melonized distributor gear.  The pressed on iron gear is common on cams designed for retrofit applications.  Crane Cams uses -IG at the end of the part number and Comp Cams uses -8 to denote this.  I'm sure other manufacturers have a similar numbering system which will denote a pressed on iron gear directly in the part number.  

My understanding is that when the OEMs started switching to roller cams they were using 5150 billet steel.  GM started using meloinzed distributor gears because they were building flat tappet and roller engines (sometimes for the same vehicles) side by side.  This allowed universal distributor gear compatibility regardless the engine's cam (example, a TBI engine had a flat tappet cam while a TPI engine may have had a roller despite using the exact same distributor and being offered as options in the same car).  Ford it seems didn't do this.  They matched the distributor gear to the cam in the engine, using steel gears on roller cams and cast gears on flat tappet cams.  How they avoided confusion is mind boggling, since they were still building flat tappet engines in trucks until 1995, a decade after they first started using roller cams in cars.  This would lead me to be very wary of the distributor gear on a stock Ford distributor vs a vis cam compatibility.  Therefore, if you have a 5150 billet cam you need to run a steel or melonized distributor gear, unless the cam has a cast iron gear pressed onto it allowing it to be compatible with a cast iron distributor gear (though a melonized gear would also work).  Such a setup would be an aftermarket only deal.  OEM cams are always a single material.  

If the cam is 8620 billet steel (I've only ever seen roller cams made from this) you have to run a sacrificial gear, either aluminum/bronze or composite, unless you get an 8620 billet cam with an iron gear pressed on.  8620 billet cam cores are typically reserved for pretty radical combinations.  They use 8620 billet steel to avoid snapping an iron or 5150 core from high spring pressure.  The soft distributor gears used in these applications are designed to be sacrificial.  They wear out so the gear on the cam doesn't, and what they drop into the oil as they wear isn't hard enough to cause damage.  It seems composite gears last longer than aluminum/bronze despite being softer.  Such a setup really isn't meant for the street, at least not a street car that sees a lot of miles.  These gears should be inspected frequently.  I've heard life expectancy clams of 2k-15k miles.  I would advise getting an iron gear pressed onto an 8620 cam for street use so you can run an iron or melonized distributor gear.  

In order of harness distributor gears go from melonized to steel to iron to aluminum/bronze to composite.  Melonized means the gear is salt bath nitrided, which is a surface treatment/hardening process (some cranks are nitrided).  What is counterintuitive in this situation is that you can pair the hardest distributor gear with the softest cam material.  Apparently the nitriding process doesn't just harden the material; it also prevents cam gear wear allowing it to be used on a cast cam.  So my thoughts would be, when in doubt go melonized, unless you have a 6sally6 race cam made on a 8620 billet core!

If you can clean the gear on the cam and the distributor gear, you could try and use some layout dye, etc. on the gear to see if the contact is even or biased to one side by installing the distributor and cranking the engine through a couple revolutions.  I'm betting something isn't centered.  The gear is getting pinched on one side and has too much clearance on the other..  Since the interface stays the same its only wearing out the teeth on one side.