So I talked to my dad and he changed the plugs over winter to a RJ18YC Champions. The car was running super rich with the 850 demon and I messed with the MSD distributor at first timing was 18 degrees at idle 36 advanced with lite springs and pulling 9-10 inches in vacuum. Changed out the spacer for the advance so now timing is 28 degrees idle and 36 degrees advanced and the car runs way better now with an idle around 850-900rpm pulling about 12 inches of vacuum, car drives like a new car, no kidding. Now my question is should I run the colder plug and my buddy says since my dad is running a digital 7 box we could lock out the distributor for 36 degrees at idle and retard the timing on the msd box. Would running a colder plug with the timing locked out would that make a big difference running and performance wise? We also mix a combo of non reformulated 91 fuel with leaded 110 race fuel. Also this car doesn't have any vaccuum advance or power brakes.