1966 Chevy Truck Ignition

HI, I've recently purchased the old beast and did a little work to it. New platinum plugs, new accel 8mm wires. New cap and rotor. I replaced the points with a Pertronix module. The coil was replaced with a Pertronix Flame thrower coil. After all was done I started the engine. Seems to run fine until I put a load on it. Then it starts to lose powerand misfire, even backfiring through the carb.

I removed the coil on the advice of a friend and the engine runs better and smoother. He believes the coil was just too much for the stock cap causing it to arc.

I would like to add the coil back to improve the engine performance. What can I do?

Thank you.