Is the "Proform" unit from them or is it a later Mopar Perf unit? Just curious.
IF the car starts and runs fine until it stops running, should not be any reason to replace the entire distributor unit, unless you just want to. Check the circuits with a volt/ohm meter and see what works before and after it stops. THEN you might find where the open is in the circuit that stops the engine.
Also, for general principles, check the "big red wire" on the inside of the bulkhead connector. That feeds the ignition switch. Make sure its connector is firm and tight, but still removeable.
It might seem like an "it was ok the last time I looked . . .", but clean the battery posts and the inside of the terminals that attach to it. After I installed the MP electronic ignition kit on my '67 Newport, it started and ran fine, for FIVE starts, but on #6 start attempt, nothing. Everything was still connected and no evidence of anything wrong. A new starter relay did not change things, either. THEN on more serious looking, ai saw a thin coating of gunk sneaking out from between the terminal and batter post. I removed the cable ends and found a coating of gunk on them, which would otherwise have been not seen. After cleaning the cable ends' inner surfaces and the posts themselves, END of problems.
An aftermarket electronic voltage regulator?
If you do not have the FSM, you can download it and carefully peruse the wiring schematics.
Just some thoughts,
CBODY67