A buddy of mine's dad has a 5.0 in his Jeep Commando Rockcrawler, and it has plenty of power to turn the 42" Iroc's he's got on it. It's also very easy to wire up. Ford's fuel injection system is FAR superior to any GM system of the same era. Gm's is basically a carb with 2 injectors on top, and is very difficult to make work correctly and is in my experience, marginally reliable at best. There is just as much stuff available for the 5.0 as there is for a chevy 350.
For simplicity sake, go with a 3 speed auto. Simple, strong, and readily available. If you go overdrive, make sure to get the Ford AOD tranny and not the AODE. If you decide to go 5 speed, the T-5 that came in the Mustangs is a pretty decent unit. The one's that came in the trucks are manufactured by ZF, and I've only heard that they are junk.
It's good to have somebody consider another alternative with a motor swap other than a chev 350. They have been done to death, and are SO boring to me at this point. HTH man. Let me know if I can help in any way.