Now that i'm thinking a little clearer, I'm not called half tanked for nothing, you might have gotten away with your cr on the little ford because of the duration and overlap. On my old street stock, I had angle milled,fully ported aftermarket heads with flattop pistons, and I couldn't even test run it on pump gas. Yes , a retarded ignition would help, but to me it seems like pouring dollars in only to drain them back out. Most of my engine building has been for stock cars, but just think of what kind of power it takes to run a 1/4 mile with 4 turns in 15 seconds,with a 2 bbl carb! I know aluminium heads will allow more cr as will smoothed and coated pistons, and un-shrouding valves to eliminate hot spots will give you a little more. Then you need electronic ignition and fuel injection o2 sensors and a computer,which will allow some more. You could also play with rod length, which if you lengthen gives a little more time at tdc for burn to occur, works good on sbc, haven't played with too many fords. Hank