Count the teeth on the starter motor pinion first, see if there's the same number. Measure the diameter of the mounting holes, and bolt pattern. Other than that there's no other easy way to compare them.
I know that they're the same as far as electrical wiring goes.
Whoops, I was thinking starter motor for some reason.
If it physically fits then it should work fine. The plugs are different but the wire colours are the same. You can take the pulleys off the front of them and might be able to swap them over if you need to.
The only difference on the electrical side of things is that the CA alternator is a 70 amp, KA is 80 amp output.