I wish I was closer so I could help. This makes no sense. Can you take some pics of the block surface and the starter surface? I went back and looked at the flywheel pic. You never touched it, right? Are you using the front mounting bracket? It usually disappears over time. Is there a longer threaded end of a bolt sticking out the front of the starter? There is a short steel bracket that mounts to the block and to that single longer bolt head. It gives support to the motor end of the big fat Pontiac starter. Plenty of guys get along fine without that bracket but the factory felt it was needed. When you say it kicks the back down that bracket may prevent that.