Trouble keeping it running in gear , how many Rpms does it drop in gear versus park , you mentioned vacuum leak - Did you spray looking for leak

Factory single point distributor , with the 1971 electronic retard box on distributor ?


I would bee looking at dwell versus timing versus points versus distributor springs especially if factory original


Distributor intermediate shaft and rotor position versus spark plug wiring order

Timing set position dot to dot , double check if you only replaced the camshaft

Sounds like your overlooking something simple

Torque Converter would have been the last thing I would have thought of based on what your saying