You didn't say what type of distributor..is it a points style or electronic? I'm assuming you have Accel stuff which is very good.I'd be suspect of the coil,expecially being that old.

FWIW.... I still use a Chrysler/Mopar race ignition system that has been in the car since 1981,it works fine and I see no reason to change it.

Nautilus Racing-
We use Superformance gaskets and Turbo Action converters/products.