From my experience.. When I did my L67 swap on the Lumina I installed a TC that I got from the owner of the motor. The trans was perfect before the swap. Put in the TC, within 5 minutes of getting the car started it staretd whining bad in park. Took it for a drive, it started banging gears bad and start shuddering when the converter locked up. Then i had my brand new trans flushed/rebuild
When I picked up Nates GTP late last year the TC was whining after 30 minutes of driving. Ran perfect though. No banging gears or nothing. pulled the pan and it looked like used motor oil.