Aluminum heads with a low compression 440 will loose compression? Huh?

Aluminum absorbs the heat faster, taxes your cooling system more, and the absorption of heat is supposedly a power loss because instead of the heat pushing the piston down it is being absorbed by the head. Like said in couple posts above you would need exact aluminum and cast iron heads and some serious equipment to measure/prove the theory.

As far as putting aluminum heads on stock stroke engine with intent of building stroker bottom end later I would be concerned about getting the desired compressions ratio right. If compression ratio is desirable stock stroke then might need custom pistons when the stroker bottom end gets built to get desired compression. Where as if heads were selected based on off the shelf stroker kit you could select head chamber sized accordingly.

Also pay attention to combustion chamber quench and head gasket thickness.