1972 Demon 340 engine mods

Its all in at 3500 rpm, which I think kills power in lower rpm under 3000.
At what rpm it would be best to have full advance?
Generally, no.
But with no vac advance, you can bring it up much earlier - especially if drag racing - since the engine is relatively cold (compared to a long distance haul or a stock car or road race).
But even with drag racing, if the weight actually hits the stop too early, then timing can retard in the upper rpms.
Some links here about that
Mopar orange box retards timing?