Hello TC,
Page 7-5 of the Rev. 4 G5 installation manual shows how to wire the RS-232 #1 output of the Aera 660 bare wire cable to a G5 to provide lateral and vertical navigation guidance to the G5.
If you configure the Aera 660 RS-232 port #1 to "Aviation In/NMEA & VHF Out", and connect the blue wire to the RS-232 input on G5, SL 40 and TT autopilot, you should be able to drive all 3 devices.
The "VHF Out" part of this transmission will allow you to select a frequency on the Aera 660 airport frequency page and send it to SL 40, and the "NMEA" part of this transmission provides navigation guidance to the G5 and autopilot for a direct-to or flight plan.
Since the Aera 660 has 2 RS-232 ports, this will leave the 2nd port available to connect an ADS-B traffic/weather receiver like the GDL 39/39R/50/50R/52/52R.
Not exactly your equipment group, but it shows both RS-232 ports in use.
Let us know if you have additional questions. It is best to email us directly at the email shown below for specific wiring questions.