RK-24 and RD-24 difference

[AR52]

Hi there,
I have 2 motors, 1 of which is a 1962 40 horse RK-24 that runs but doesnt shift, and I also have a 1962 40 horse RD-24. Im hoping I can steal the shift solenoids from the RD to get mine going.
I cant find anywhere what the difference is between these 2 motors?
Thanks