This isnt the important part, this may help you to help me, I have a 1983 305 that was in my camaro but put it in a 1984 Gm pickup, Automatic tranny, and i had it going, it ran BEEutiful, it purred, but the tranny in the gm had been worn out, it took a second for Reverse to kick in, but then one day, it was cold, i had to rev the engine to keep it running, so i put it in reverse and reved it alittle and it made a CLUNCK noise but it stayed going, then another time i tried it and it would kick in so i reved it alittle, nothing happend, i was facing a Mud pit, so i decided well i gotta get going, so i put in in D and and went, i left a 600 ft straight stretch of just torn, ripped grass and mud, then i tried reverse and it grinded like Hel* i put it in par or Neutral it grinded, so i left it in the driveway, Yes the tranny is dead,

IMPORTANT PART
the tranny is disconnected, When i try to start the truck all i get is a THUNK, i have good starter and that crap, come to find out it may be hydrolocked, well took the Spark plugs out, it cranked over like never before, so i left the cyl's open to let them dry, well 5hrs later, went back put plugs in, and it started but you had to have it to the WOT posistion, it would bog then start to scream and lock Right up, i mean like it hit a brick wall, it would squwak and vibrate everything, so i tried to crank it and THUNK, I repeted this process 5 times then decided, i'd wait till i got my garage built and rip the engine open..

 

you probably bent a valve, or if worse case -- a rod.

Take a looksy at that. Just take the valve covers off and see if you can spot anything out of the usual.

 

Like a broken crank