firehawk496

i got my car all back together and im having some major flywheel/starter issues with the car. It was a firebird with a t56 and is now a th350. I bought a 153 tooth flywheel which i did count and conferm and im using my stock starter that had. The only way it enguages is if i put like a half an d inch of shimms in it. The it will stay in the started and not pop back out. I dnt know if i now need a 168 tooth or what. Please let me know what you did your set-ups. thanks.