Fuel pressure dropping while driving and under acceleration to zero at idle runs 4 lb electric Blue

You could put 8 four barrels on there and a 3/8 feed would still be enough if you have the pump, lines, tank and all associated parts plumbed correctly. It’s not how many carburetors you have. You aren't making enough hp to need more than a 3/8 line. We’ve told you how to fix it, stop micky mousing stuff and do it right.