Rusty, the W-1 is an excellent carb choice for running duals. Over the years carter kept making improvements so the later ones are a better choice then the early ones. 1941 - 1946, #483's and #574s are what Jon recommends and is what I am using. They are basically the same as the 1949 you have only with the easier to find accelerator pumps. I would hunt down two of these instead of a second '49 model.
Purchase a manifold with the smallest runners to keep the air speed as high as possible. Clifford would not be my first choice. Use stock jetting and carb settings for the carburetor you choose, not the engine it's going on.
On the exhaust system, use exhaust heat if possible to heat the intake, water heat works, but is slow to come up and doesn't get as hot. Stick with 2" or 1 3/4" pipe into a dual inlet single outlet muffler for a mellower tone, true duals sound bad ( in my opinion ) on a six cylinder.
Joe
