Back then I used a pair(the thinnest, weakest set) of springs from a Mr. Gasket kit, I don't remember the kit number now though
Those springs would pull the advance weights back under 1100 RPM and be at full advance by 1300 RPM which made the motor start well and t was like having the distributor lock out almost.
It took me a while to figure out how much initial to set that motor up with so it would idle well and not kick back on the starter, it would start to kick back at 18 BTDC would really kick back at 20 BTDC 13 BTDC or less made it not idle well