I bought mine and it already had a Kolher in it. The drive shaft is on the flywheel side. It looks like they parted off the spline shaft from the onan mount and welded it into a kohler mount. They had put a new clutch on the kohler that was made for the kolher. The motor mounting holes have been redrilled and the electrical adapted onto the kohler.
If I had the time and money, the only change I would make would be to get rid of the original drive shaft and splines and go with a regular one and standard V pullies.