Low compression ignition timing considerations...

Lower compression can handle more timing,40-45 degrees depending on cylinder condition,and lower fuel grades would help,to a point.As long as the motor is tuned and fueled correctly,it should run great on regular fuel.Each car is different,and tuning is a big key to making it run 100%.Running 93 octane fuel will cause a very slow burn,as a lower grade fuel causes a faster burn.The secret is what is right for your car,only you can tell by trying each level of fuel and tuning it,mrmopartech