What should I look for in an overhaul kit?

Your best bet would be to call up a company like CHP, Keith Craft, etc. and talk to one of their tech guys on what they'd recommend, and why. You could probably do a simple hone and re-ring of the stock pistons, but you wouldn't get AFR 185's on without cutting larger valve reliefs.

If you were looking for a refresh and new pistons, then the pistons would need to be decided on, based on the size of the combustion chamber, compressed thickness of the head gasket, deck height clearance (how far the pistons are below, or above the deck), and how many cc's the piston's dome displaces (-18cc, or whatever like you had listed above). You need to have a certain compression ratio in mind when figuring that out, or at least a general idea. It's not rocket science, by any means, but it can be the difference between the piston smacking the underside of the cylinder head because of improper deck height, or having an 8.1:1 compression ratio because it turned out you didn't want -18cc dished pistons. That's probably all clear as mud, right? Here's a pretty decent compression ratio calculator that should give you a decent estimate: Engine Compression Ratio (CR) Calculator

Floating wrist pins are when the small end of the connecting rod is bushed and uses spiral locks in each side of the piston to hold the pin in place. On a factory rod, the pins are pressed into the rod and require being pressed back out, as well. With a floating pin, you can remove it yourself without the aid of heat, or a press.

I'm honestly not really in a position to be able to make any recommendations for pistons otherwise. I'm definitely not a professional engine builder, I just understand the concepts and have helped build a handful of them. I've not done the research necessary to put together a combo and fire it up, which is why talking to someone in the know would be a good thing.