I thought that too so I pulled the dizzy and cleaned the base and scraped and brushed the block to make sure it was good clean metal. That's when I dropped the shaft though, so don't know if that was it yet.
I was refering to the ground wires in the engine bay, did you remove them to detail? if so go back and make certain they have a good connection, I just pulled a ProCom dissy out of my car and replaced it with a Pertronix and wow what a difference!! no more sputtering and missing, and all this time I thought it was the carb.
Guess someone either inserted the oil pump driveshaft upside down or removed the stop washer. The washer is there so it will contact the block when removing the distributor and keep it in place.
Got ya, and yes when I panted I left my grounds unpainted and went back with a test light to double check them before reassembly. Yep, washer was removed by one of the previous owners.