You sure about that Ed? I thought it was just the early SB's that had the small register?? The input shaft spline changed count on everything in 68 but I'm pretty sure I remember putting a 72 or 73 727 behind a 66 383 with no problem. If the register size was different I wouldn't have been able to do that. That was over 30 yrs. ago though so my memory might be fuzzy.:scratch:
