Any number of 3 speeds 3 speed OD and some 4 speeds. Probably a pretty safe bet is anything from the early '60 back. I bolted a Y block infront of the 3 speed in a '62 unibody. Pulled the 6 out and bolted the y block in, the bell houseing even matched. I had a full syncro 3 speed behind a 312 (same block) I ***ume that it came from an early mustang or the like.