Couple 46rh questions

Will still require same amount of cutting because OD unit is where the issue is. Both OD units are the same physical size. The A727 fits an A body tunnel, and so will the front 3 speed part of a 46RH. Its tighter fitting there yes definitely, but the problems with both are where the OD unit is. 42RH gives you more space to run the TV cable up to the carb IMHO