What he ^^ said.
Does it move in any gear? What kind of noise is it making? It could have blown out the center of the clutch disk. That happened to me once.
The tranny is pretty dynamite proof, so I wouldn't worry about that.
You might also check the driveshaft, although for the truck not to move, that would probably be hanging on the ground.
First truck -- 1929 Model A Ford pickup, restored from ground up. Wish I still had it!
99.5 F250 PSD Supercab LB 4x4, ZF-6 w/SB Con OFE, 3.73LS, Boost & pyro gauges, Swamps S175/146 injectors, DP 80 HP Econo PCM (classic version
), AIS, coolant filter w/"hokum" bracket,
regulated return, heated mirror mod, lighted cupholder, Marinco heater plug-in.
Hard or no-start? Check Here