273 Conversion Questions?

I don't think you would have any trouble running pump gas on a motor with the Egge domed pistons. If you run a perma torque head gasket and don't mill any more than necessary to true everything up, you'll have trouble getting much over 9:1. I believe Toolman landed at 9.22:1 with .030 over pistons and after milling .030 off his heads.