If you go to www.kohlerplus.com
and click "enter as guest" you can look up the service manual for the Kohler engine. That should give you a wiring diagram for the engine. You could try looking up the craftsman tractor on www.craftsman.com
and see if they have a diagram as well. Then you'd be able to just hook the proper wires to the proper places. One thing to watch for is if either engine has a fuel solenoid on the carburetor. If, for instance, the Kohler has it and the Tecumseh didn't, then you will have to run a wire for that to get power whenever the key is in the run and start positions. Do you have some pictures of the engines in question and the connectors where they plug into the tractor harness? Model and Spec numbers on both engines would help too.
'56 IH 350 Utility Gas, '47 Farmall H Gas, '08 Bobcat Toolcat 5600 Turbo
Pineray Dairy (RIP) -- 1880-2015 5 generations and 135 years of quality milk production
Stihl, Ariens, Tecumseh, LCT, Lauson, Kohler, Subaru and Lawn Boy Certified Technician with over 15 years experience.