Good point, I hadn't thought about that yet. So the thicker head gasket won't affect the stock lifters and pushrods so much, but will it throw off the intake alignment? Or would that also be okay?
The thickness of the gasket won't matter. You have to remember that these engines have manufacturing tolerances that can "stack up" and there's enough built into the process that allows for "stack up" (an actual industry term) so it all bolts together and runs.
If you look at a lot of things, valve stem and rocker wear, varying valve stem heights, crappy rocker arm stampings, cam base circle diameter variances, and on and on, you'll see that the lifters are capable of compensating for quite a bit of variances.
Regarding gasket material, the composite gaskets will seal better and will not need to be retorqued. They will compensate for irregularities in the head and block surfaces. When (if) you pull the heads, you'll see dark spots in the steel gaskets, especially between the cylinders, where combustion blow by has started. I don't think I've ever seen a factory built 440 engine come apart that didn't have those black spots, just some worse than others. I started using composite gaskets when FelPro came out with the Permatorque (sp?) line back in the 70's. Never had an issue with them.
If you are worried about losing that slight amount of compression, the thing to do is have the heads milled to compensate. Taking .020" off is nothing, and having the heads resurfaced is part of doing the job right anyway. A lot of places use a purpose made belt sander to resurface the heads, so strapping them to the milling machine might cost a few more bucks (or is it Euros?) but that will take care of both straightening and bringing back the compression. Really though, IMHO, it's not enough to worry about for this engine.