This one is a 1955 Bel Air (Canadian production), equipped with a dual Fenton intake and headers. Our shop built a pair of Rochester model B carbs for the owner. It took a lot of tuning to get these to run right – I think the he may still be tweaking these.
With this set up there is less manifold vacuum at part throttle, so you need to shorten the power piston springs to keep the carbs from getting into the power mixture under light load. Also, the jets need to be on the large side because of a weaker vacuum signal (due to the larger venturi area). As well, the carbs should be synchronized. Finally, you have to consider that Model B carbs came with various sizes of power channel restriction – essentially a fixed jet that determines how much additional fuel flows when the power system is engaged.
Another one I really got a kick out of was the GMC COE truck. These are getting as rare as hen’s teeth. You sometimes see Chevrolet Cab-Over-Engine trucks, but not so many GMC’s, at least not here in the Great White North.
Notably, GMC trucks like this usually used a Zenith updraft carburetor while the Chevy versions used a Carter BB updraft. Of course the reason for the updraft carburetor was because of clearance around the engine. This is why these continued to use updraft carbs until 1962, while GM cars had gone downdraft by 1932.