I normally dont cut the heads to rasie compression but deck the block. Or change the heads or pistons. Angle milling or cutting .050 is not going to do much of anything. I was thinking 10:1 or higher compression and a lot more cam. Would be needed to come close to the 450 hp numbers wanted.
Cobalt.... Emissions are lowered because lower compression engines use less fuel. A lower compression engine can run very lean air fuel ratios and still make good power and not knock or stumble. A higher compression engine will need more fuel and more acc pump just to not knock and not stumble when you punch it. So one more time slowly so you can understand lower compression equals less fuel which means better mpg and less chance of knocking running with less fuel. This is a fact.
Modern engines are different animals. They run super tight and use much better cooling and materials. They are also capable of running with water temps over 300 degrees. An older engine would not be very happy at those temps. And need to be cooled with alot more fuel.