as long as both are long tail shaft 727...no you do not have to mod the shaft
they will have the tranz mount in the same place,so shaft should be the same
I just bolted a set of sb 727 lines to a BB 727 and they fit perfect
I had to cut/weld the torque rod bracket for the shifter(bolts to tranz ear)
but I used a short shaft MH tranz,had to move the xmember 2" forward with it,tranz mount was 5" from main case
stock long tail 727 the mount is 7" from main case
I have a 71 BB 727 long tail that will bolt in the truck correct and move the xmember back to the stock location
the engine mount will move on the swap not the tranz mount
