As I recall Vince telling it, the kickstarter seal itself might not need to be replaced. It might be fine.
The cover plate that locates the seal has several bolt/screw holes in it that currently position it.
These holes in the engine that the screws thread into are not always located in the right place.
If they are mis-located, they will locate the cover plate in the wrong place for the seal to line up with the kick starter shaft.
The rubber seal can take some misalignment but if it is too much, oil will leak out.
This can be corrected by enlarging the screw clearance holes in the cover. It doesn't take much to make the holes big enough to clear the threaded fasteners so that the cover/seal plate can allow the seal to be the thing that centralizes the plate rather than the mis located screw holes.
If you do this little "fix", just be sure to let the rubber seal position the plate and then make sure you don't move the plate when you tighten the screws.