Cam advice for ill advised 318 combo?

Milling heads .020" in your situation is an absolute total waste of money. It takes about .075" to make close to one compression point difference, so .020" is a drop in the bucket. Best thing you can do is sell those heads and buy some 302 castings. That will get your compression close to or possibly over 9:1 with thin head gaskets. The 302 heads will be a much better match for your 318. They will have the correct size ports, smaller, closed chambers to raise compression and the valve sizes will be a better match. Shouldn't be too difficult to sell those 2.02 heads.