Is it worth it?

I've tried the 1 bbl vs 2bbl thing with my dart and the 2 bbl definitely out performs the single bbl holley. I used an Offenhauser 4 bbl manifold with some home made adapters so I could run a 1920 Holley 1 bbl or switch to a Carter bbd 2 barrel without changing manifolds. The Carter 2bbl gave better throttle response and had more top end power, the Holley 1bbl just kinda "runs out of steam" over 3k rpm, both carbs were in good working order. The mileage actually stayed the same between the 2 carbs. I would much rather drive a slant 6 with a 2bbl carb than one with a single bbl carb.

Just my two cents..