I don't have the answer to your question, but I can tell you how I got help when looking for an oddball u-joint to mate up my driveshaft to my pinion yoke.
I went to a local driveshaft shop and these two young guys searched for half an hour for the u-joint I needed.  Then the owner (older and more experienced) got back from lunch and solved the problem in two minutes.  He took a u-joint that fit the driveshaft and a separate u-joint that fit the yoke.  He then took the larger caps that fit the yoke and swapped them on the the u-joint that fit the driveshaft (the inside dimension of the caps were the same)... thus making a custom u-joint.  Of course that meant that I had to buy two u-joints instead of one, but it was still cheaper than having the driveshaft ends changed. I saved the part numbers of those two u-joints so I'll know what to buy in the future.

I'm not sure if all that makes sense or not.  If not, check out this old post.  It has pictures that make it a little more understandable.  http://members.boardhost.com/MustangSteve/msg/1350269998.html

So, if you have an experienced driveline shop near you it might be worth stopping in and chatting with them in case they have an experienced guy like the one I stumbled upon.
 

I did the t5 conversion last winter.   I found the correct yoke I needed and measured the for the driveshaft and took the Drive shaft and yoke to a shop to shorten along with my measurements.  They figured out the U joint thing and I was good to go.    I put the new yoke in the t5 and pulled it out 3/4" and messured this way below.  

I just installed a aluminum driveshaft that I got out of a 98 Exploder 2wd. It had 1330 u-joints on both ends. I removed the stock yoke and got a T5 yoke for the forward end in the 1330 size. I got a conversion u-joint for the back end that had 1330/1310 as my rear end yoke was a 1310. I had to shorten it about 2 1/2 inches to fit the 4R70W.

Don't know yet - gotta get the transmission fully installed and wire in the controller. Gonna be a little bit before I know.

So today I scored an aluminum driveshaft from a 97 4 door 2WD Explorer at the pick and pull.  It's about 50.5" long from the cap centers, which is really close to my stock 65 driveshaft.  Had to go thru about 5 before I found one that wasn't bent by the fork lift.  One tip: If you can't get the rear yoke bolts off (12 point 12 mm), just remove the outside C-clips and pop out the U-joint.  Mine came with 1330 U-joints on both ends.  Since my T5 yoke was also a 1330, I used a stock replacement for the front.  Since my 9" has a 1310 yoke, I needed a 1330/1310 combo U-joint in the back.  Post some pictures tomorrow.  Thanks to everyone for their help, esp. Michael H. for his old write-up - really helped.

My original 66 Mustang yoke fit just fine with the T5

jkordzi wrote:

Michael H. wrote:

I don't have the answer to your question, but I can tell you how I got help when looking for an oddball u-joint to mate up my driveshaft to my pinion yoke.
I went to a local driveshaft shop and these two young guys searched for half an hour for the u-joint I needed.  Then the owner (older and more experienced) got back from lunch and solved the problem in two minutes.  He took a u-joint that fit the driveshaft and a separate u-joint that fit the yoke.  He then took the larger caps that fit the yoke and swapped them on the the u-joint that fit the driveshaft (the inside dimension of the caps were the same)... thus making a custom u-joint.  Of course that meant that I had to buy two u-joints instead of one, but it was still cheaper than having the driveshaft ends changed. I saved the part numbers of those two u-joints so I'll know what to buy in the future.

I'm not sure if all that makes sense or not.  If not, check out this old post.  It has pictures that make it a little more understandable.  http://members.boardhost.com/MustangSteve/msg/1350269998.html

So, if you have an experienced driveline shop near you it might be worth stopping in and chatting with them in case they have an experienced guy like the one I stumbled upon.
 

You mentioned in your old post that you got an aluminum driveshaft from a 97 explorer 2WD V6 and that it was about 50 7/8" from the center of the caps.  That is within the range I need and it looks like it has the 1330/1310 U-joints.  I think I'm going to go looking for one tomorrow.  Just have to figure out the interchange to maximize my opportunity.  BTW, I see you didn't use the original damper/balancer on the yoke.  Any vibration issues?  Did you have it rebalanced?  Any clearance issues with the larger diameter?  Thanks.

Sorry I'm a little late answering...
I have a vibration issue but it's not because of the driveshaft.  The whole reason I was swapping in the larger aluminum shaft was part of trying to get rid of the vibration...and it actually dampened the vibration some.  I've pretty much ruled out everything except the transmission.  I have a lot of slack in the output shaft of my T5, so I think that's the culprit.  I have a rebuilt T5 on order from Glen... so hopefully I'm right and that will solve my vibration.  I did not have it rebalanced because my local driveshaft shop won't balance aluminum shafts, but it's probably not a bad idea if you have a local shop that will do it.  I didn't have any clearance issues with the larger diameter driveshaft.
I'm glad my post actually helped someone.  I've gotten so much help here, I'm glad to be able to return the favor!