Anyone happen to know the part number for Kinslers stumble valve?

There may not be a part number. As I recall they were custom made for each application.
Oops! Was thinking Engler. They made one for my Fontana while I had it on the chassis Dyno at Willies carburetor shop

Most of their parts are shown in the catalog with P/N,

http://kinsler.com/index.php/handbook-catalog