I'm not the guy to ask about fuel/air mixing. That's a little beyond me and more of a dyno guy type thing to ask somebody. I'm having a hard time visualizing what you're talking about but would love some pics.

I'm not sure how far you've gotten or if you already have the supercharger purchased but I would look into manifolds from these guys if you don't want to do the custom on-off type setups for a lot of $$$.

http://www.aussiespeedshop.com/product/chevy-6-inline-supercharger-kit/

Also, I would suggest opening a thread like I have here for your build to centralize your thoughts and create a log of what you've done/are doing so you don't get them mixed up in threads like this.

69 Buick Special Deluxe. Intercooled Turbo Chevy 250 @ 15psi on a stock long block. It's kinda fast.