Garmin has received FAA Supplemental Type Certification (STC) for the GFC 500 digital autopilot in additional aircraft, including the Cessna 177/177A Cardinal, the Beechcraft T-34A/T-34B series, and the Piper Seneca PA-34-200T and PA-34-220T II-V.
Source: general aviationGarmin autopilot certified for Cessna Cardinals, Beechcraft Mentors, and Piper Senecas