The largest carburetor you can fit on stock Vespa moped cases, the Dellorto SHA 13.13.
Has the lever choke with a hole on top. If you have a later style Vespa, they often had a rod that stuck into this hole for easier choke use with the body panels on. You can also just use the choke as-is.
The carburetor top on some of these say Spaco. That is totally normal and how they come in original Dellorto bags.