Detonation Problems

[rico7769]

Team,

I have a sb350 (3970010) hooked to a TH400 (auto) from a 77 Chevy in place in my 67 GMC. We are running 305 heads (54cc) and have a decked block (not sure how far, but the vin plate isn't there anymore). We have been having detonation issues since we got the truck. Based on the block/head combo we are probably running ridiculous compression #'s but I don't know if that is contributing to it or not. Nothing under 2500rpm or so, but only over and at heavy load on the motor. Carb is new, dizzy and rotor new, plugs and wires new, and fuel pump new. We also run 93 octane and include booster in every tank. Everything seems to be set correctly according to specs. We are total timing of around 33. The issue is this, we have a high plane manifold (aftermarket of course) on the truck and the vacuum advance from the dizzy hits the manifold limiting the amount of spin we can put on the dizzy. Is there a way to get rid of that vacuum advance and switch to something more efficient w/o going to a comp controlled system? Any input would be grateful. We recently put in a new pressure guage on the fuel line and found that we are consitently running around 10psi when we should be at 6-7. I don't think that would have anything to do with the detonation issues though. The mixture on the carb was set with a vacuum guage and we are standing idle at around 900rpm. Not looking for a high end race truck, but would like to get on it every now and then so I'd like to get this worked out so we can finally move on to body work. Thanks,
Steve