The Garmin GFC500 and GFC600 is very very close to universal. Each aircraft install is different of course, but the GFC500 I know for a fact can be fit onto multiple types of Cessna, Piper, Mooney, Cirrus, and Beechcraft aircraft. Each type is different, but there are airframe specific kits and manuals that outline exactly how sheetmetal and avionics go about fitting and installing the autopilot system in its entirety.