You could use something like the Aera 660 to drive your non-Dynon auto-pilot (e.g. TruTrak) and link the 345 via serial or Blue Tooth to the 660 for wx and traffic.
If you have a Dynon system, you would want the Dynon AP servos, transponder and GPS 2020 antenna plus the new ADSB-472 for an IN source of wx and traffic.
Lots of Q&A on the ACS site, where the ELT question has already been posed.
Q: My ELT (an Artex ELT 345) needs GPS position information via RS-232. Can the WAAS-equipped GTX-345 supply that information via one if its serial ports?
A: Garmin recommends connecting your ELT with a GPS such as the Aera 660 or GTN 650.
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Ray
RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, Dual PMags, Vetterman Trombone Exh, SkyTech starter, BandC Alt (PP failed after 226 hrs)
Catto 3 blade NLE, FlightLines Interior, James cowl, plenum & intake, Anti-Splat -14 seat mod and nose gear support
All lines by TSFlightLines (aka Hoser)
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