mill heads and maintain proper valvetrain angles

Milling doesn't affect pushrod angle. Or valve angle. Or geometry. Only pushrod length is affected, along with the position of the intake bolt holes. If you have to mill the heads a lot you have to mill the intake mounting flanges on the heads too. If you go really far, then you can;t mill the intake flanges on the heads far enough (you hit the valve covver bolts) and you have to mil the intake itself. By the time you're done you'll have a bunch of $$ in milling and pushrods - and frankly static compression ratio isn't that big a deal.