440 source heads on a stock 440

I think that cam you mentioned is too big. It won't be great at lower rpms. It'll run, just not great. You could advance it for more torque but that's a band-aid for a poor combination of parts.

I was gonna do a similar thing with the 400 in my truck. I looked hard at those heads but decided it wasn't worth the cost. I have a lo-po factory short block with the pistons a mile down in the hole and 452 open chamber heads. The guy I bought the truck from put a .484 purple cam in it, Performer RPM and Holley 750. The combo was poorly thought out, makes very little torque at low RPM which is exactly the opposite of what the truck needs with the NP435 truck trans and a 3.23 gear. Aluminum heads would have done nothing to help it. I got a milder cam and a regular Performer intake for it but have yet to install them.

You could use the .020" shim gaskets to bump the compression up a tad but you're still going to be under 9.0:1.

When you look at cam specs, the cam companies will usually give an optimal combo for the cam, like "minimum 9.0 C.R. , 3.23 gears, dual exhaust, 750 carb" etc. The key in this case is obviously to look at the compression ratio recommendation for the cam and see if it fits.

Maybe look for another cam that makes more torque at lower rpm and can be used with lower compression instead of the heads. You need pistons more than heads but that's a whole new short block. No easy answer.