Dump that distributor for an advance Only distributor at salvage ( you want the Good advance Curve ) >
Run as much advance as you can depending elevation just set and drive it until you get
Pinging or Top end miss he back it off 5 degrees or so They like a lot of advance .
Get a solid copper (inside ) coil wire to dist for a good Hot spark > NGK Plugs work best
Make sure your heat risers are opening > 16 tho. is best Point Gap & use Point Lube also consider to convert to electronic ING
Unless You run the motor every 2 or 3 Days the flue drains down often in those carbs making it hard to start quite often>some install
an electric pump at the rear and turn it on and wait a Min or so before starting >it will run much better with more advance and a distributor swap ( Most any advance Only type will work and fit ) That Retard Returd was a smog deal they are junk