Barstart - What model 30 are we talking? .. the 'S' or 'PS' series Thirty .. or the later 6G series 30/R4?? ..
According to the 30/R4 service manual, the early 6G series machines up to S/N 6G1588 were fitted with a packing-gland style water pump.

I don't have parts books for either tractor .. and my Edition 7 (1947) tool guide doesn't list water pump wrenches for any tractor or engine .. even though it lists all service tools back to the PS models ..

The only info that I can find, is .. the Cat Tool Guide shows a picture of a 4A334 water pump wrench .. with a notation .. 'for use with early type water pumps" .. it appears that this wrench, was a universal-type water pump wrench .. I hope this helps ..

The`re are 2 sizes of nuts 2-1/2 part#1B1909 other is 2-11/16 #S702

Water pump wrench number 1B1909 has a 2 ¼” opening.
Kelly