I'll send some pictures when I run by my house today. When I DO remount the 1920, I'll adjust the float level and see if I can't get fuel flow after adjustment.
as to the exhaust manifold, have you checked the operation of the heat riser flap (aka the butterfly in there). make sure it's not froze up and restricting flow.
one gasket only. likely the "rough cut" thicker looking one is the one you want. but bear in mind certain carbs have specific base gaskets and you could be inducing an airleak by mixing and matching pieces around.
The "rough cut" one was one of two that came with the 6145. I don't know. I bought the 6145 kit from o'reilly's (walker kit), but mike's carburetor parts' kit for the 6145 doesn't come with the thinner gasket that's the same size with the same cutouts as the rough cut one.
