First, you have not told us what plug you are running. There is no reason with that compression you should not be able to run a NGK XR5 type heat range. Something elso is not right here.
What is your ignition system? In order run more advanced timing you need to make sure you have a good ignition. I would start there. I had a very similar combo and actualy had 10:1 with 452 heads and ran 36º total timing.
That MOPAR cam is not helping you out at all. I would consider a change to more modern cut like Lunati Voodoo.
