I swapped out my Harmon Radio for a Kenwood marine radio and installed it on my '10 Ultra. It has interface for thumb controls so that part should be good. My problem now is what I can do with the 2nd plug from radio that is used for CB and Coms. Is there an interface for the plug? Any guidance is appreciated!

 

When going to an aftermarket headunit the second plug is no longer used and the components associated with that plug are no longer usable.
You can either pull the wiring harness apart and remove the plug and connect wiring or just tuck the plug out of the way in the fairing somewhere.

 

I zip tied it up under the new HU.