I have owned a 78 f150 4x4 supercab,351m,4-speed, for 10 years before I traded it for a mercedes diesel,and sold it. I just got a f250 supercab 4x4,camper special,400m,c-6,
that I plan to keep for a plow/wood truck.
My f150 drove all over with no problems with the engine,even cross country pulling a trailer, parts are cheap for these old trucks, a 460 will bolt right up as the bellhousing is the same as the m engines, and you can pick up a 460 for well under a grand, they get better mileage and about 60 more horses.
I traded my dodge diesel for 10g cash and the ford and a 97 chevy 4x4,
my 92 f350 cc idi aod should be up here soon.
you can't beat those old fords for a solid work truck,they are really useful when you are wrenching on your diesel and need to get around.