The output of the DG to the autopilot is not really standard. A lot of
DG's have no output at all. Get the DG that will be compatible with
your future autopilot. Contact STEC and get the specs. It makes a
difference, you need to make sure you get the right one.

Having said that, I would urge you to consider an autopilot that does
not use a DG. STEC makes them. They work very well. The big advantage
is if you loose vacuum, your all electric autopilot continues to work.
Big safety factor in IMC. Such autopilots have a "wings level" mode
where you point the plane in the direction you want, and then decouple
it. The plane just continues to fly the straight ahead. They also have
a feature where you can make slight corrections ("trim" the autopilot),
and use the autopilot to turn the airplane, by turning a knob on the
autopilot. It works well. Such autopilots couple to both the VOR head
and the GPS (they get their left and right from the indicator dial).
These autopilots are less costly, less complicated, don't require the
more expensive DG and work great. They continue to work without an AI
or DG or vacuum.