Good morning, I am presently running a 77 400 with what I believe to be a 067 cam. I will be replacing it with a 76 455 with all the same bolt ons with the exception of ported 6x=8 heads and a ram air 3 (744) camshaft. My question is how much will the cam change affect my off idle performance, will I lose a lot of power below 1500 rpm or will the extra displacement of the 455 make up for it? I am asking because I presently have 256 gears and 2.64 first gear. It performs well now but driveability depends on the low end torque. The carb is 800 cfm Q-jet, stock 71 Gto cast iron intake and ram air 3 exhaust manifolds with 2.5 exhaust with X=pipe. Thanks in advance.