The Kohler # shows it to be a 1976 build. There are Troy focused web groups out there which may be more helpful. Congrats on your purchase! I know if it were mine I would start by seeing what shape the carb is in and getting it up and running just to get a feel of things.

Thanks for the update - my plan of attack will be cleaning or replacing the carburetor, then tracking down a tire! This unit is actually looking better and better, since finding out how old it actually is!

There is an excellent Troy Bilt Tiller Club in the Yahoo forums.

I've never saw 2 belt with 7 hp engine allway been 4 speed with one belt but I don't know everything about troy bilt horse.

The older ones of this vintage have two matched belts-later ones had just one belt. I have a '75 or '76 6hp that I restored this last summer. The carb was the worst part to clean up-it was totally gummed up. The engine only needed new points and a plug to get going again (well, and a new head gasket,too).
The main shaft running from the lower pulley to the tines had very excessive play in the bearings,and I had to get shims to get rid of the play. The front seal needed replacing,too.
Be sure that the gear oil you use in the transmission is compatable with brass gears and bushings.