[Gunner]

I don't know much about jets in multi-carb setups, but 60 sounds about right for a 450 - you'd have to use the usual plug check for lean or rich, or a F/A meter, to adjust them sensibly. A 6.5 power valve is probably close enough - I'd guess it might come in a little early and rich, not a problem except in tweaking for max power. Also a problem for final tuning, though, not off-idle performance. If you're seeing reasonable performance once you're past idle and no strong lean/rich indicators, I'd worry about jets and the PV later.

I think you'll find a squirter size increase and cam change will help a lot. Try that, and making sure your idle settings are optimal, before you mess with anything else.

If you have an MSD distributor, it's pretty trivial to change out the max advance stop for the 18* one (largest in the standard set). Then you can run 18-20* initial with no problems. Even with iron heads, FEs just love a lot of advance - LOTS more than SBF or most other engines.