Nice.
I'd watch the gaskets: I understand gasket sealing compounds (such as permatex) are dissolved by ethanol.
Are the vents on your carbs accessible? The vent is about having atmospheric pressure at the surface of the fuel so the right amount is sucked into the venturi, not about passing air or vapor in and out.
I'd be tempted to hook up a few inches of alcohol-proof tubing with a screened end, to retard the diffusion of moisture-laden air into the bowl when shut down (without affecting the pressure or minor back-and-forth air flow when operating). Something like what you sometimes see on a utility gas pressure regulator when it's indoors (to sample the air pressure outdoors and keep any gas that gets through a failing diaphragm from causing the house to explode). I'd turn the end down to avoid dirt and dripping condensation entering the tube, but keep it essentially level so it wouldn't form a siphon and suck fuel out of the bowl and dump it somewhere if the bowl level gets too high.
