Well I figured that would be a 2 second Google search--WRONG!
Seeing how I like really old stuff I kept searching. There seems to be a consensus that Kohler never published the info prior to 1965. I did find this one page that is interesting. Go 1/3 way down and try that link. I can't tell if it is for everything or just generators. If it is just gnerators, apparently Kohler still built them way into the 70's.
http://www.oldengine.org/members/die...ler/Kohler.htm