I recently bought a used ‘68 302 after my 289 dropped a valve and ruined the block and head. Because of the differences in the two motors, I swapped the harmonic balancer and water pump to accommodate the inlet and outlet of the radiator in the ‘67. Needless to say, timing this engine has been challenging. I have timed the engine close enough for it to start. Two big problems though, the first is when I try to put it in gear (C4 Auto) the motor dies or backfires and barely has enough power to back out of the driveway, second when it warms up to operating temp I can’t get it started again. I turns over real slow. Is this still a timing issue or something more?