A bodies used the same length Automatics as the B, C, E bodies but the 4 speeds were shorter so the driveshaft for the auto will be shorter than an original 4 speed in an A body.

Nearly all 4 speeds use the same yoke as the 727 but IIRC there were some A bodies that had the same yoke as the 904 transmission. If my memory is correct then I believe it was the later model feather lite & the overdrive A833's. You should check the yoke size before you have the driveshaft shortened or made.

Like somebody said the 1970 oem pilot bushing does not effect the torque convertor. Only the later model and aftermarket ones that sit in the torque convertor register hole.