Wes, my Gizmo modded K-30 came with a modded 257 carb. The number is stamped in the casting on the side where the fuel inlet elbow is located and toward the flared end of the carb.
Wes, I'll have stock 257 and 929 carbs and diaphragms and some rebuild parts with me when I get to Evansville. You can rummage thru my parts boxes! The K-30 may need more stuff than a stock carb can supply, but you are welcome to experiment.