Who would of guessed? ME!
The front of that engine is the flywheel end, the rear is the pto end. No matter if it is on top,in a vertical application, sideways or longitudinal mounted,--- or cub decided to drive off the flywheel end.
No harm done, if it was time to replace one, it is time to replace the other, and you already have one now.
Now if you happened to removed the crankcase cover while changing the PTO seal and it had a paper gasket between it and the block, replace it with a paper gasket. If it had RTV as sealant use RTV to reseal it. Make sure you put the seal in deep enough so the centering tabs on the PTO clutch have a place to fit into. but not too deep. Use RTV sparingly if you use it. More is worse not better,---- ALWAYS!!
As it gets into oil passages and clogs them causing catatastropic engine failure.
FWIW: Kohler wrote the service manual/parts lists for their engine, no matter who purchased it and installed it in various ways.