On three of my front-engine dragsters running SBC with a factory short tail housing PG into a 9" rear end, I purchased from Auto-Zone, one U-Joint that would fit the PG yoke and the 9" flange. With this setup, alignment is critical and assured by sliding the PG yoke back into the 9" yoke with no caps on and rotating the rear wheels. If perfectly aligned up, down, and sideways, it will not push the U-Joint forward when rotated. Put the U-bolts on the 9" flange and its good to go.
I was told that this would be good for rails running 7.50 and it worked like a charm for me. Cost five years ago for the U-joint was less than $15.
Another off-subject tip was to use a 70's VW Bug steering box. Great ratio, easy to mount, and the price was right.
Dave