440 detonation issue

You've never mentioned what heads you have.....unless I missed it. So...if you have open chamber heads already, changing heads will do you absolutely no good. The thing to do is what I have been trying like almighty hell to explain to you. Diagnose the thing and go from there. There are so many variables here, it is impossible to tell without having the engine torn apart to look at what all is there. Also...here is another scenario no one else has thought of. Carbon buildup is a major player in older engines that can cause an increase in compression and also cause just the symptoms you describe. Have you dribbled about a 12 ounce glass of water through the carburetor while running the engine at about 2K? Doing this will burn off any large carbon deposits in the combustion chambers that may be hanging out and raising compression and blow it right out the tailpipe. If that fails to make a difference, try the high octane swill and see of the detonation goes away. Also think of this. What would a simple, all out basic rering cost you? I am sure with all the knowledge you've displayed asking questions and whatnot, you can rebuild it....if you haven't built some engines already. Hell, I bet you could get buy with everything for under 300 bucks less cam and lifters doin a basic rering yourself. Why? So you can SEE the inside of that beeyotch and know what's there. You can blueprint the compression ratio and see what you really have. a TRUE honest to goodness flat out 9.0:1 engine WILL have problems running on today's premium with a short stock duration camshaft. I had a friend who had a numbers matching unrestored 1971 330 HP 350 LT1 Camaro when we were in school. That car had a sticker on the sun visor that said "USE PREMIUM FUEL ONLY" and that car was built was in 1971. It had MAJOR PROBLEMS runnin on anything other than pump premium in the early 80s. It absolutely LOVED 114 Cam2. Those cars "only" had 9.2:1 compression from the factory. A lot of people don't realize it, but an honest anything over 9:1 is pretty damned high.