3 speed to 5 Speed

[flatbedchev]

I am finally gonna dig in on my truck and the first thing I want to do is make it highway friendly. It has the original 3 speed, 3 in the tree trany in it and I'd like to replace it with a 5 speed. I remember reading that you can use a 5 speed from an Astro van or S 10 to back a V8. Does anyone know which ones will work and which ones won't? I think the input shaft on the 4 cyl and 6 cyl trannys are different
any ideas?
Oh and my 350 is pretty much stock, so ther should be no worries of it breaking anything loose in the 5 speed. I've also heard they can't hold up to a lot of HP