Hi Folks, hoping for some help

I own a troy bilt tiller purchased new back in the 70's (unsure of exact year). Originally a 7hp Kohler Horse model, SN 197252. Model number unknown. During the first ground breaking this year the transmission developed a bad leak at the front belt pulley. Upon dissasembly I discovered that the main shaft had over 1/4" of end play which destroyed the front seal. The rear tine bronze gear was very worn and the gear oil had a definite gold hue. Also the rear bearing for the main shaft had disintegrated and chewed up the back end of the main shaft. At a minimum I need the the main shaft, bronze gear, and all related bearings and seals.

Now my questions: To get the proper parts if available I'm told I need to know the model number which I don't know. Also when rebuilding this transmission what is the allowable main shaft end play (if any) and how is it adjusted?

Thanks in advance