I have a 96 single cab f-150 300cubic inch motor, inline6, and I'm wanting to do some mainline work on it. I was think about putting a crate 5.0 mustang engine in it and put a slap shifter in it. I was wonder what I would need to do with the rearend and what y'all's thoughts would be?

 

Your going to need a donor engine harness from a 5.0 equipped truck. And convert to MAF, OR go Carbed. Depending on if it's stick or auto, need a standalone transmission controller. Such as quickus1/baumann to use.
Also you will need the oil pickup tube and oil pan from the 5.0/5.8 truck.

Expect to spend about 6000
Source- My Orange one is a crate x306 from ford racing.