No. If I understand you correctly you want to put the PG in your 51. The PG links up to an open driveshaft. Your 3 speed has a different end on it, one made for a closed (torque tube) set up. You would also need a differential set up for an exposed drive. If memory serves me there was a PG that hooked up to a torque tube but in car.
Getting the rear end changed is not major because a centre section from a later model (56 and later) will bolt right in.
