It is actually a Zama that is on it at the moment, but I am probably going to put a Walbro of around 9 or 10mm venturi on it, as I want to try the engine on Gas/Glow fuel, and I have had problems with Zama carbs in that application.

I would say make the adapter manifold match the carb and the engine. Blend it all so there are no steps to interrupt flow.

I used the spring out of the original rotary carb in my fuel pump. It is a bit stronger than one would think is necessary, but it works. Be sure to put it on the correct side of the diaphragm. It needs to be on the same side as the vacuum pulse, so that after the vacuum pulse pulls the diaphragm down, the spring flexes it back up.

AV8TOR