Proper jet size for a 1920 carb?

Chrysler used 6 different Holley 1 barrel carbs in 1973.
The R-7031 is a Holley replacement for all 6 of the original part numbers.
Let's say you went into a store that sold Holley carbs in 1978 and gave them any one of the 6 numbers stamped on the original carburetor. The Holley replacement would have been R-7031 for all of them. Most likely that is the original jet.