Yes, but please note the following considerations.
For the S-Tec System 20 or 40, these systems are roll axis only. However, if equipped with a GPSS converter, these systems will follow the lateral steering commands from the GPS for a WAAS approach. Vertical guidance is pilot controlled.
For the S-Tec System 30 or 50, these systems are roll axis and altitude hold only. However, with a GPSS converter, these systems will follow the lateral steering commands from the GPS for a WAAS approach. Vertical guidance is pilot controlled.
For the Systems 55, 55X, 60-2, 60PSS, or 65, these systems will track the lateral deviation from the GPS navigator in the Approach (APR) mode and the vertical deviation in the Glideslope (GS) mode. If you are using a 55X or other autopilot systems equipped with a GPSS converter, they will not couple to a WAAS approach in GPSS mode. To follow both the vertical and horizontal deviations of a WAAS approach, the autopilot must be in Approach (APR) mode and Glideslope (GS) mode. The 60PSS system is pitch axis only and will follow the vertical deviation in Glideslope (GS) mode.