Budget 318 build

The caution on this is that .040" off the heads in one particular engine may be fine for the original pushrods, but it cannot be guaranteed to work on every single engine. There are 4-5 variables at work, and some sets of parts will be near the operable adjustment limit from the factory, and the extra milling will push one or more lifters past the limit.
maybe... never seen it. Can't buy a head gasket as thin as the approx. .015 original tins. So ya give back .010 of the .040 even if the .027 "thin" gaskets are used. IF the "over the counter" Fel Pro's are used, they are .050 thick. Now it's a gain of about a whopp'n .010. Many cut 'em .060 and never an issue. I wouldn't raise an eyebrow to .040.