Whatever the best case you can find, that will be fine. You'll end up doing the same work to any case regardless. Grady's much more knowledgable than me when it comes to many things, cases included.

I'd wait until you have decided on crank, rods, heads first, then worry about cylinders last. It doesn't take me any time to whip something up, if I don't already have it on the shelf. Pistons would obviously vary depending on many variables, so decide your whole engine first and get everything else lined up first.