Dual carbs on a stovebolt are either "one too many" or "one not enough". They're mostly eye candy to impress people who look under the hood and don't realize what a mistake the engine builder made. Unless you install two very low CFM carburetors you'll be running lean enough to cause lots of backfires, and maybe a fire under the hood caused by backfiring and collapsing the carb floats, followed by massive flooding. There might be a limited reason for dual exhausts, but at least do the old school modification of splitting the stock manifold instead of eliminating the heat riser and ruining the performance of the engine during cold weather operation and/or warmup.
Making "improvements" to the intake and exhaust system on a stovebolt (or any other) engine without also doing internal engine modifications such as installing bigger intake and exhaust valves, porting and polishing the cylinder head, installing a radical camshaft profile, increasing the engine displacement, and compression ratio is like joining two log chains with a paper clip. All you do is waste a lot of time and money, and end up with an engine that loses power, or at least doesn't increase it nearly as much as you are hoping to do. At one time, I had a couple of hundred dyno run records filed away to support that idea, ones I had complied in around 20 years of engine building and dyno testing in a big public high school auto shop in Nashville Tennessee. My advanced level students were participating in a program sponsored by a few racing team owners at the Nashville Fairgrounds 5/8 mile oval track. They provided the funding, and I trained students to build and dyno tune NASCAR specification short track engines.
