thoughts on the edelbrock sp2p manifold

Think about how the runners create that high velocity... restriction. The manifold does not "move" the mixture faster, nor will it "make" more vacuum. Vacuum at idle is a function of cam duration and overlap. If you want strong vacuum, don't go nuts on the cam.

Since it sounds like you have the SP2P now, waste a gasket and bolt it on. Use a 500 CFM four barrel and enjoy near stock type performance.

If you don't have the manifold yet, buy a used Performer off eBay, or use a factory iron intake, you'll be happier in the long run. The performer is superior in every way. Add a 600 CFM carb and enjoy a nice upgrade.

If you want to run dual 2 barrels, get your head examined. Even if you insist upon reinventing the wheel, why start with a square rock?