u need an "A" type bell housing to make it happen. use tht bellhousing on ur gearbox.
i think T50 from year 70++ has shorter gear shifter housing position.if not mistaken, it's abt 4"-6" shorter.
so ur's might b the older version. if ur's is the older g'box, and now u use newer version T50, (later 2T, 3T, 4A, 3A....), u might need to cut a hole for ur shifter coz they r longer.
but the shifter housing can be swapped over oso i think.
it's not easy to get the bell housing...might as well get the "A"type T50, and keep ur's as spare.
read sifu chin's gearbox change:
http://www.my-acoustic.com/Car/gearbox/T50/T50.htm