Thicker head gaskets/ less compression...

The old adage that aluminum heads effect compression is an old wives tale. Couldn't be further from the truth. 10:1 with iron heads is 10:1 with aluminum heads or 10:1 with wood heads. All things equal, cylinder pressure will be the same regardless, so compression is totally and completely unaffected. Where the difference lies is Iron tends to hold heat in, while aluminum tends to dissipate it. That extra heat dissipation does absolutely not one thing to reduce compression. Nothing. All it does is allow the combustion process to run a little cooler. Nothing more. That is the only reason you can get away with more compression using aluminum heads. That's why an iron headed motor will spark knock before an aluminum headed motor.

Also, like I explained to you in my PM, that Mopar 509 cam does not map anything like it is advertised. It's well noted that Herb McCandless mapped all the Mopar cams back in the day and none of them came up as advertised. Mopar used a completely different measuring standard for their cams and most of them fall well shirt of that on the degree wheel. Herb himself found that the 509 only measured at 242* duration @ .050 rather than the 248.5* Mopar says it is. No telling where the intake closing is either. Obviously since you're having the detonation issues, it's a good bit sooner than the 74* Mopar says it is. That would be a HUGE hydraulic cam....and the 509 IS a big one, but it aint that damn big.