The K lobe profile is more "pointed" with less duration. Shorter.
The KHK lobe is more "wide" and lightly taller (more lift)
McFarland made a shaft for the KHK cam. The gear teeth (on the KHK cam) are narrower for less resistance and quieter operation.
I fixed up a set of cams for Kevin Baas' KH racer.
A guy(reputable source) told me when the 1956 KHK came out, and you took the engine apart, the cams were marked 1KHK, 2KHK, 3KHK, 4KHK. If you wanted to "hop-up" your KH or K Model, and went to the dealership to buy a set of KHK cams.....the cams were marked 1,2,3,4. The KHK profile is the same lift and duration as the first KR cams (in 1952 and 1953). You can look at the Enfield Racing website and see a chart with the various cam lift figures for reference.