I have an RJ-58 that has the K90 4hp Kohler on it. The Clinton motor was original to the RJ's, but I think they would have been earlier than 1958. I believe they would have been known as Ponds? You could be looking at an RJ-35 model. I'm not knowledgable on Wheel Horses like I am on John Deeres, so I'm only tellling you what I do know.
As for the serial tag, you will find it decaled to the left side frame rail (while sitting on the tractor) just behind the grille. I can't tell you the break points for each year, but I'm sure someone else will be along shortly.
The guards that you want to see on the tractor, and not missing are the muffler guard and the transmission drive belt guard located on the right side of the tractor, just below your thigh while sitting on the tractor. These guards can be rather pricey if missing. Having fenders included with the tractor would be an added plus.
Edited by johndeereelfman, March 03, 2013 - 05:33 PM.