Mr fix it, you are correct in that some motors like only 30 total like mine. But, I am running yates heads and 12 to 1 compression, so the combination is very efficient. I doubt that a lower compression big block with any heads and 2 carbs is as efficient and in my experience they need closer to 38 to 40 degrees of timing to run there best. Not to rehash the plug reading thing but the very best way to get the best read is, new plugs, warm motor, second and third gear flat out, at top of third with foot floored, shut off motor, coast to side of road, pull plugs and read them. If you guys saw my plugs after a day of around town driving or after some use, the read looks like a way too rich
oil burning mess. Now, new plugs, flat out on the race track, shut her down, they are text book in color. The only other way is with the use of a wide band o2 on a rear wheel dyno. good luck, scott.