390 w/10/1 comp & 2.080 intakes

>>Am afraid of detonating this thing to death, and I don't want to over lean either. <<

Because LEAN causes HOT and it's more likely to detonate with over-lean mixture and higher heat caused by a lean mixture.  But the cam, valve size, intake, etc. aren't what determines if it's running lean or rich. That's your carburetor - jetting and so on. 
Run it too lean, it will run hot. 
Run it hot it's more likely to detonate. 
Octane is the RESISTANCE TO SELF IGNITION and nothing else. It's not how slow or fast it burns, it's not how rich or lean it will run. 
So if you can get 91 or 93 octane, that resists self-ignition better than say 87 or 89. 

I solved the detonation issues with my 70 Javelin 390 by replacing the radiator with one that had been COMPLETELY redone - rodded, cleaned to perfection. It never really ran all that hot "by the gauge" but obviously it was hotter than it should have been - perhaps the flow was slowed enough it developed hot spots. I also noticed that the 4300 Motorcraft carb caused less trouble than the Edelbrock carb I ran on it most of the time. (Motorcraft had superior venturi design)

There's a whole lot of forum members who live in that part of the country with the goofy gas formulations that run these engines without trouble - best to let them chime in now. 

The key to making good useable power to is have a lot of air speed. Putting a big valve is nothing more than putting a bigger hole in the head. When you do that on the type of application your asking about all you'll do is slow down the air speed and your power output will suffer greatly.

Tom