I had encountered the same thing. The coil needs need to be located in correct position to get the good air gap (it is better with the coil set up ring (ID = 4.468″). I got this number from the web and made the ring. It worked well. Then you need to set up the timing correctly. Forget about 0.020″ gap, just go with timing by the multimeter method and get the spark right away! But just make sure the condenser is good first.

I have an aluminum tubing with 6″ OD and 4.0″ ID. I slide it 1.25″ thick and put in the lathe to bore out to 4.468″ ID. and clean up both sides to make it look good. You don’t need 1.25″ thick, It could be 1″ thick. If you don’t have tubing, just use 6″ x 6″ x 1″ or 3/4″ plate and bore out the ID. It does not look good but square plate with this ID could serve the purpose.