Not such a conundrum, actually... unfortunately RM does not support the older style drive ring anymore. The (sort of ) good news is that the new versions are much more robust and a better setup all around.
You may get away with just buying the drive ring and motor - the motor drive cable and connector are unchanged.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"