Try this- - - - -put the transmission in 3rd. gear, and gently try to roll the truck back and forth. Don't force it- - - - - -if something has locked up, it might be possible to roll the engine backwards a little. Watch the fan while you're doing this, and it should be obvious if the engine is moving. If it rolls backwards, try to get one full turn of the crankshaft. If something expensive has happened to the bottom end like a broken connecting rod, etc., it will probably make less than a turn before locking up in the other direction.
Jerry
