Well, a 383 is not going to like all that fuel so you'll likely want to jet them down a mile, a better combo would be a pair of 500cfm Edelbrocks (1803's). They are factory calibrated for small engines and mild dual quad applications. You will have all of the same linkage, air cleaner, and fuel line issues to deal with but it seems that in your case (custom) that's less problematic.