My "A" body and Van (truck) has the same length tail shaft. I always heard the trucks had an extra clutch plate as in the Hemi (HD). The 727 were a strong transmission to start with. So, I think the internals were the same for SB and BB cars. Short and long tail shafts set aside. The 4-speeds in the "A" bodies were short with only one shifter mount, as the "E' and "B" bodies had two in the 70's. Not sure before the 70's. I would think only one mount for the "B" bodies because there were no "E" bodies then.