70 challenger 4 speed, 3.54 gears, full weight, 440 .060over, 4.15 stroke, flat tops 11to1 comp with edelbrock heads just polished up not flow test, holley street dominator, 950hp carb, 2inch hooker headers, hope to run on pump gas. .045 quench. Would like a solid mech cam which size would be best? I was thinking MP557?

I'm no expert by any means, but I have a combination very similar to yours and have a Comp solid with 247/255 and .549/.572 on a 110. Very happy with it in my car. Best bet is to call one of the cam gurus on the site and tell them what you have and what you want to do. I'm sure someone will chime in with their contact info. It's really the best way to get the engine to run it's best.