Hey there new truck owner here I'm just starting to learn.

My transmission blew a seal yesterday and found out that wasn't the only problem and now I need a new transmission. I need a c6 7.5l 4x4 3 speed for a 460 engine but I'm having a hard time finding one and all i can find are 4 speeds. I'm wondering if its possible to put a 4 speed in instead until I can find someone to build a proper 3 speed. Any help would be great thanks for reading.