Engine still not right after timing set

He said it had something to do with attaching the machine and not having room with the headers. But it doesn't look like its necessary as it appears to be a voltage issue. Says he got the car to run pretty well at first then it starts having issues after driving it. He measured around 3-4 volts (i assume with engine running) at the coil and said it was very hot. After letting it cool off, it ran ok again. He wants to replace it with an msd ignition system; ditching the ballast and mopar ecu altogether but keeping the existing distributor.

The good news is, he pulled off the carb and checked that out and said it was clean and everything on it was good. So at least one thing I've done myself was correct.

I don't think your "mechanic" knows what he is talking about

If he really did measure 3-4V that is LOW and either is loaded down by too much current---which might indicate a shorted coil------or too low because the supply to the ballast is low. That might indicate a wiring problem in the harness, AKA bulkhead connector, ignition switch, etc.