Is this the side where you fixed the broken crossover pipe stud? I wonder if the scorched wiring you found was at least partly the hot manifold.
From what I've read, excess unburned gasoline will overheat the catalytic converter, not the exhaust manifold. I think the hot manifold is a result of a LEAN condition as others have mentioned.
Older 460's got "EGR Plates" added, between the Intake Manifold and the Four Barrel Carburetor. This provided mounting for the EGR valve and the needed port back into the engine. The thick carburetor insulator gasket was on top and there was a thin gasket under. On ours, the Plate rusted to the mounting studs and the thin gasket blew out underneath. Lean condition. Ran better with both gaskets new and the connections cleaned up so tightening the nuts at the carburetor tightened the whole stack.
I also read that "older" 460's developed intake manifold gasket leaks. Again, lean condition. You may be able to spray carb cleaner, even WD-40, around the intake areas with engine running. If it "finds" an intake leak, you'll hear it in how it runs.
