So just an update and a little info about what is possible with the stock intake and exhaust manifolds.
I’m replacing the 10:1 451 talked about earlier in the tread. That engine did push my 68 Road Runner to an 11.63 @ 119.
The new engine is a 499” with 14:1 compression the same heads intake carb and ignition from my 451. Cam is a moderate solid roller designed by Dwayne Porter. Intake is extensively worked with the sharp turns removed and rounded. In legal form on the dyno including air cleaner but no alternator or mufflers pulled over 560 hp and over 570 ft lbs. testing spacers, carbs and other stuff I don’t want to talk about power and torque were much better. Bottom line is 600+ hp is available through the factory iron if you do it right.

Bill