I have somewhat the same problem, when i try and start the car all you hear is the gear on the stater grind against the flywheel, i rebuilt my engine, the block was an auto tranny block, but my car is a 78 5speed, don't know if that makes a difference at all, my connections are brand new, battery is brand new as well, i am currently on my 4th auto zone starter, and this is driving me up the wall.
... i forgot to add that the flywheel i am using is the original.