It depends how long you cut the old gravely gear.
Say you cut 1 inch before the gear.
and the engine crank is 3 3/4 long
Then you have 4 3/4 inches plus the gear is 5/8 thick =5.375
So 5.375 from where the engine mounts to the end of the gear
not counting 3/4 dia. end that goes inside of the bushing.
The gear sticks into the transmission 2.135.
The Kohler adapter is 1/2 thick and the part that stick into the Transmission.
2.135 plus .500 =2.635
So 5.375 mins 2.635 =2.740
Or make 2 adapters 1.370 thick each
Now you cut your gear 1.625 plus the gear is .625 = 2.250.
So your engine is 3.750 plus 2.250 = 6.00 long.
6.00 minis the part that sticks inside of the transmission 2.135 =
-2.135 =3.865
So you would need 3.865 spacer out side of the transmission.
I hope this helps double check my figs I can be off.
Thanks Bruce g