Beams, is your application an unusual swap; why not a factory ball and trunnion drive shaft? I imagine a number of members have some original pre-'65 flange shafts of various lengths available, as I do.
I have an 8 1/4 rear. I never really looked into length difference between 7 1/4 vs 8 1/4.
I figured that even if I could track down a B&T driveshaft (assuming it fits), it would probably need to be rebuilt. So there’d be cost to purchase (and probably ship) plus rebuild. I didn’t actually do the math, but figured it would be close to a wash.
