75 GMC C15 rear u joint too small

[hillytim69]

I am converting my stepside to a th-350 with a 1 pc driveshaft that i got from another '75 Chev swb donor vehicle. My truck originally came with the sm-465 4 spd with a 2 pc shaft with a center carrier bearing. I got the th-350 in and put new precision 369 u joints on my 1 pc shaft. Then when I tried to put the shaft on the rear axle yoke, I found my rear ujoint to be at least 1/4 inch too narrow. The rear axle yoke on my truck is bigger than from the donor truck i got the shaft from. I'm not surprised because everything on my truck is heavy duty for a half ton. i just need advice on what to do. Do i have the driveshaft modified to fit the bigger joint or replace the yoke on the rear end with the smaller one ( if i can find one at the junkyard). Would the pinion depth be affected if I remove and reinstall a different yoke? Or is there a special u joint for this situation? i can't imagine a ujoint that is wider one way than the other, seems like it would be unbalanced. I'm sure this is a common question on here but I couldn't find quite the exact info I needed on my searches. I sure am getting antsy to get this thing ready to fire up for the first time and any help i can get to point me in the right direction is really appreciated.