I've always found the Carter / Edelbrock carbs to offer the ideal blend of economy and performance .
Holleys are decent carbs , but they seem to be a carb which needs constant attention , which is annoying on a street-driven car .
Remember : Edelbrock's carbs are -updated- Carter units : AFB ( Aluminum Four Barrel ) and AVS ( Air Valve Secondary ) , and were O.E.M. to our beloved MoPars !
The ThermoQuad was the right carb at the right time . Gas quality was dropping tremendously ; emissions-reducing caca was ever increasing in its presence , which means higher engine operating temps in order to help burn-off offending chemicals ; and the O.E.M. Holleys and AVS carbs were aging at that time .
ThermoQuads defied conventional carb thinking : an 800 cfm carb on a 318/340/360 street engine ? 850 cfm on 400/440 ?
The 1971 340 is arguably the best year , as the addition of the T-Quad brought its power up .
It was supposedly refactored to 310 h.p. in racing sanctions !
But , again , as usual for me , I divulge .
Go with -- imo -- a 600 cfm AVS ( a/k/a "Thunder Series" ) Edelbrock .