If we could see the harmonic balancer it would help. On the back side of the balancer there will be a counterweight.
If the counterweight covers almost half of the circle, it is 50.  If it covers about a third of tge circle it is 28.
Go to summit racing and look at their balancers for part number ending in 289 and part number ending in 302. It should show a pic of the weights. The 289 is 28 and the 302 number is 50.

6t5klassic wrote:

Not having much success with locating relevant numbers anywhere on the block. Not able to see any counterweight on the flywheel. The only numbers i can see are the ones in my picture i sent when i removed the starter motor. I have 3 bolts in the crank pulley, but don't think that is the best way to confirm a 28oz. I'm probably going to take a guess at 28oz and order the transmission kit based on that. If it turns out incorrect, then the shop will have to swap out whats needed. Thanks for the help here. Obviously this would be easier if the engine was out of the car.

If I'm remembering correctly, Ford went to the 4-bolt balancer prior to gong to the 50oz balancer.  Check the size of the weight on the balancer as MS suggests.

Wow i really appreciate the help here! I just got out of my garage and here is a little more data to go on-
With the starter motor removed, and cranking the engine by hand at the crank pulley, I got the following numbers (stamped not cast) off the flywheel as it made its way around - E6ZR-AA. I know there are also cast numbers but they are so hard to see. My preliminary research seems to show this as 50oz, but still not 100%.

50vert - i am sorry but don't know about a conversion balancer. Some of this is beyond my mechanical ability.

MS - yes, when i spin the flywheel manually, i can see the counterweight. Is there a number of teeth that it would span? I know the 50oz weights cover longer area than 28oz weights, correct?

BobE - I have 3 bolts holding on the harmonic balancer. How do i confirm the size of the weight on the balancer?
 

You have 1 bolt holding on the balancer, and 3 bolts holding the crank pulley to the balancer. Remove the crank pulley, and look for another 4 bolt holes for a 4 bolt pulley.
A conversion balancer has both bolt patterns, and usually, an interchangeable weight to suit both 28 and 50 oz engines.
I'm gunna guess you have a 50oz motor, cos it's a F1SE
 

Last edited by 50vert (9/06/2023 7:38 PM)

I did not take off the pulley, but seems that is my only way to know for sure? I was able to get a small scope through the starter motor hole to read the stamped numbers on flywheel, and seen this -
E1ZR-6380-A2A. That also does not seem to be definitive. I'll attach pics of crank pulley, but likely will not be helpful if i need to pull that off now to see the balancer behind it.
 

I think he has an aftermarket 50oz "conversion" harmonic balancer.   Cj still offers it, and I found another seller of one that had the initials pj stamped on it.   So, they are out there.   Seems to me the reason these became available back when is when people started putting later model 5.0 in their Mustangs, the pulleys still lined up.  Because the pulley doesn't have that 1/4 4 bolt nose on it.  I spent some time digging, I could not find a factory 3 bolt 50oz. 

  https://www.cjponyparts.com/cj-classics-crankshaft-damper-conversion-3-bolt-with-lip-50oz-mustang-5-0l/p/CSD51/?gclid=EAIaIQobChMIisG1sfKZgQMVqvGUCR18YgKaEAQYAiABEgLy1fD_BwE

Think Greg B nailed it.  Looks just like his.

Consider using the MustangSteve cable clutch setup with your five speed. It eliminates all the z-bar parts from your four speed linkage. It is a better design cable setup than the MDL unit. There are no small clevis parts that wear out on the cable.