906 or 452 which is best overall

You're pretty close to what you want. With an 85cc head, zero deck, .039 gasket and a 6cc valve relief in the pistons you are right at 10:1. With a 90 cc combustion chamber you are 9.5:1. It's not all that expensive to get a piece of clear plastic to cover the combustion chamber, drill a hole in it to fill with fluid and buy a 100cc burette so that you can measure and balance your own heads.

I never suggest using iron heads unless you just have to from some personal reason and can do all your own work on them, or the rules require you to run an iron head. Too many other good cost effective options with the aluminum aftermarket heads available now.