Should I Port And Polish?

Well, if the heads have been "worked" already, what more do you think needs to be done?

A good polish on the exhaust side and the combustion chambers, knock off the rough edges and casting flash and get it back together. Unless you plan on doing it yourself, it isn't worth while.

As for the rest of the set up....personally, I'd just put a good set of pistons in it, have the bottom end balanced and call it a day. Since the '96-'98 KB kits weren't intercooled, you're going to be limited to the amount of air you're going to be able to safely push through the engine anyway (unless you're running a steady diet of C12, or water/meth injection....which is a PITA in its own right), so there's no sense in going overboard on the top end mods, or the bottom end components. With 7psi, you probably won't see much more than about 400whp....which the stock internals should handle just fine.

If you insist on sinking money into the engine, don't limit yourself with the Kenne Bell. Spring a cooled centrifugal or turbo kit that'll take advantage of your mods. Otherwise, that 5.1L stroker assembly, cams and forged bottom end is really all just a waste of money. That small, non intercooled blower will never let you take advantage of their strength, or horsepower making capabilities.

Its your money, but since you're opting for the Kenne Bell kit, I'm thinking you're look for more of a fun daily driver, than a race car. I've been there and done that with the modular scene and if I could do it again, I'd only spend money where its really needed.....on an upgraded fuel system and a good dyno tune....then call it a day.