Maybe I can muddy the crystal ball.
The early KT17's had a slightly smaller seal on the flywheel end.
Kohler learned that they had problems with the crankshaft in heavy duty applications, like skid steer usage. ( among other problems)
Some snapped the crankshaft as flywheels are like gyroscopes inasmuch as they resist change in motion, and a application like skid steers are something that is anything but stable usage.
SOOO they increased the crank diameter slightly in the area of the seal/and flywheel taper when the improved K T17 series II's and Magnums were built.
The series II and better yet, Magnums, were the best of that design at that time.
Today it is cost effective to assemble a "kit" of seals/gaskets covering all like models even if some are not used, than it is to stock many kits.
Inventory is money laying in warehouses/shelves.
