Denny
The K161 bore changed from 2-7/8 to 2-15/16 at Spec number 281162, which is a higher spec number than what was used in the 7 hp Cub Cadets.
There were several different recoil units used on Kohler engines, but the Cub Cadet used the Fairbanks type. They used the "3 legged" stand or mount ring and the Originals also used a 4th leg that was not part of the ring, HOWEVER, if you find a 4 legged ring (full circle) you can cut it and use it as a 3 leg. I always drill the coffin plate on the 70/71/72 and use the 4th leg, it helps stiffen it up and helps prevent breaking the 3 leg ring, which is the reason those models are usually found with the recoil unit broken or missing. The upper pulley and bearing for those models are NLA, as are the mag parts, although someone in the Chicago area was making the coils, but I have heard both good and bad about them. If you find a recoil off an Original, the spring and the pull rope can be reversed and the unit used on the 70-72 - it is the same unit, just turns one way on an "O" , and the other way on the 70-72.