There is only one carburetor rebuild kit for the IH carburetor. Of course, the Zenith carb will require a different kit. The carb # is only necessary if you need a main jet, discharge nozzle or bowl vent. These three items are calibrated as a set and the carb part number will identify what size your specific carburetor should have.
Here's where the part number is stamped. This is an example of an easy to read part number. Most are much worse or completely missing. The two part numbers for the IH carb are 251 234 R94 and 364 579 R91. Except for those 3 items mentioned, both IH carbs are identical.
Get the carburetor kit from CaseIH. The rebuild kits from TSC/Valu-Bilt/Tisco are poor quality, include only the bare necessities and tend to have pieces missing. They also have the WRONG INSTRUCTION SHEET. For the extra cost of the IH kit, you get everything you need for a complete rebuild and the instructions for rebuilding a Cub carburetor. If you also need a float or idle tube, IH still carries them.
Good luck with your rebuild - check out 'Best of HL Chauvin' for tips on fixing some common problems.