Carter/Ball carburetor- Help ID

In general, Holley's are considered superior, but they are also more finicky and the 1920 was a low-cost design and has some endemic problems. Biggest is that the sealed metering block inside gets clogged up, which makes a lean idle, and most rebuilders don't touch it, thus many bad ones in the system. Another is that the fuel bowl cork gasket is below the fuel level, so a potential leak and fire hazard. Of course, any carb can overflow fuel if the fill needle sticks open, but that only happens with engine running and usually kills it from "too rich". The BBS on my 64 slant runs it so smooth that you can hardly tell the engine is idling. The silenced air cleaner helps too.