73 spool trans mount/ Drive shaft Blues..

If its a small yoke leave it be unless there is a problem with the rear. Why open up another can of worms. The Joints small or big take the same caps. I ran many 4 speed cars with the smaller joints with slicks on and didn't have issues. Unless the pinion angle is incorrect they hols up well. My Duster had the small joints with 29x14.5 slicks 800+ at the crank 5500 converter and never a problem. When we moved the rear forward and I had a shaft made I put GM joints in the rear. You just have to control spring wrap and don't but cheap u-joints in.