Carbs
I could never get one of the factory Motorcraft spreadbores to work right on either of my 73 Cats.
BetaCat, my closer-to-stock 73 351C-4V, has a stock 4V cast iron intake, a set of early quench heads, a mild aftermarket cam and stock dual exhaust. It absolutely loves its factory Ford 600cfm vacuum secondary Holley from a 66 GT 390. I tried AlphaCat's 780 vacuum secondary Holley on it and went a half second slower in the quarter mile.
AlphaCat, the more modified of my two Cats needs the 780. It has a much more radical cam, higher compression, headers and low restriction exhaust.
Holleys are a pain (read messy) to tune correctly and are more suited to all-out performance. The Carter/Edelbrock carbs are more tuner-friendly, they don't leak and will generally give slightly better economy.