The radomes have been through at least four evolutions in the last ten years and almost without exception are not backward or forward compatible. Best man I know to talk to us Andy Chisnall at Raymarine in Fareham. What he doesn't know isn't worth knowing.
Some of the late pathfinder domes did work with the C&E classic displays but before that there was a change in cables and interface.
Sadly I think you'll have to upgrade both.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former --- Albert Einstein