The Standard Hygrade kit number for the Carter 420s carb is C1080. This kit was discontinued in 1955! Good luck on finding a Hygrade kit for this application!
When Hygrade discontinued the old "contain all" kit line in the early 1950's, and started producing the "jiffy kits", no jiffy kit was produced for the 420s. Existing stocks of the C1080 were sold, and that was that.
Jon.
