Carb tuning, larger accelerator pump nozzle?

Yea. That's the only thing I disagree on if you intend to use vacuum advance.
I would work in small steps from where you are now.
I would go for 18* at 750 rpm and make sure there is enough tension on the spring to be sure its really the initial.

With a relatively rich mixure there shouldn't be a need to light it off early. I'm running 17* initial with a 230 @ 50 cam right now. heads, compresion, intake valve closuing point all have some effect so no one answer.

Don't worry about where the idle mix screws end up. That's what they are for. As long as they have effect. If you turn them and there is no response, then they are out of working range. Four corner idle is going to be more difficult. Try not to have to mess with the secondary IFR and IAB as that will impact how well the secondary opening responds.

Thanks, kind of why I went back to 20 degrees. Probably will hook up vacuum advance but that will be down the road and factor I don't want in play right now. The idle mix screws are very responsive. I can lean it to die or choke you out pig rich with them. Seems to be they should be a finer thread for 4 corner carbs. Right now 1/2 turn from in closed sets it close enough to start and be a bit lean. One warm I set them with the air cleaner installed.