You need a known good working carburetor to break-in that engine. You will be too busy attending to other problems once you start it. Feed the gas from a clean auxiliary tank and fuel hose. Don't risk using an old rusted fuel tank. If you lived near me, I would loan you my carburetor.
Carter YF 2100 with a rebuild kit made for Ethanol is preferred but they are usually $$$. The proper model Zenith would be great if you can find one. The Rochester can be made to run decent but expect a need to rebuild it in the future (parts age warping).
