This data may help in your general understanding of Walbro carbs.
http://www.walbro.com/pdf/DiaphragmCarb.pdf

browng300
Found the 164 at their site but the screen I got did not show venturi size. Do you happen to know what it measures?

Walbro venturi size markings: "If there are two raised numbers on the face of the venturi, that is the throat size in 64 ths of an inch." per Flypaper 2