Autopilot compatibility in a Piper: Garmin and S-TEC.

Q Is it true that a Garmin 750 or 650 will not interface with any S-Tec autopilot? If so, this will change my upgrade plans for removing my dual Garmin 430 units and replacing them with a 750 or a 650 and Lynx ADSB transponder. My S-Tec 50 autopilot works very well – I am not willing to purchase a Garmin AP just to obtain the interface.

James Kadel