Garmin 430W to simple Brittain autopilot

Trying to connect a GNS430W to a simple left/right steer autopilot.

What signal wires would i need to pick up off of the Garmin?
For a VOR it asks for deflection left/right.

If i decided to add a GPSS steering unit (is this possible?) later,
can someone please explain how this type of unit works?
what signals does it take in, and what does it then send to autopilot?

thanks

I'm not familiar with the Brittain autopilot, but it's probably these connection:
On the P4001 connector (the big one):
pin 21 - Main + Left
pin 22 - Main +Right

GPSS requires a converter and mimics a heading bug. Basically it picks up the GPSS labels from the Arinc 429 output of the Garmin 430 and converts that into left/right deviation signals from your current heading. If you're old autopilot doesn't have a heading bug I'm not sure if it's possible to adapt it to work. But I'm no expert.