Input needed on engine mods

My first choice would be the later 318 casting "302" heads..They are closed chamber, have much better ports, and will accept all your rocker gear. Then I'd swap in the small Comp XE256H, and an edelbrock performer 318/360 non-egr. Paint up the intkae engine color, and run a small (500-600 cfm) carb. The heads will add a little in compression over what you have, and that will also help. You should not need pushrods. Later 273s were not solid cam. What year is your 273?