Folks I am interested in hearing from anyone with experience interfacing an advanced flight systems efis with an Stec autopilot using the st901 GPSS module.  I would like to upgrade my panel incrementally and keep the basic autopilot in place.  I believe I could still operate coupled approaches with little or no change to my existing wiring but where things get a little fuzzy is around the heading guidance selection from the efis source.  The af5000 has an Stec selection for auto pilot type.  I am not certain if it is providing the right ARINC tags to the GPSS. Ie ground speed and commanded roll rate.  Again I would love to hear from anybody having experience with this arrangement

Thanks

Tom