you need the conversion flexplate to use a 3 or 4spd auto, available many places.
The easiest deal is an early stick truck computer with a hotwire.com harness for that and a 727/518/46rh.
But you may want to have the 5, 6, or 8 gears depending on your projects. There are controllers for them and wiring from hotwire but the price goes up.