My boat is a 1976 and looking at the equipment it was installed at purchase by OYA, the importer and seller, or soon there after. The Benmar drive motor has all kinds of electronic addons that are made superfluous by the Garmin Autopilot. Hutton stripped everything out leaving just the drive. Since I had the motor serviced recently by Benmar it was basically "new". Being able to reuse the chain drive motor saved me about $1500 and great deal of installation cost. From talking to Benmar they used two types of chain drive motors with one being compatible to modern autopilots and the other not. You can call Benmar at 951 659 8510, PST, and by describing your unit they can tell what type you have. Benmar was very helpful to me and the installer. Then contact the autopilot maker and see what is compatible.
1976 42' GBC #482