"Michael" wrote in message om...

If the autopilot was optional equipment for that make and model
airplane, then the airplane manufacturer will have approved drawings
for the installation. All you need to do is get a copy of the
drawings, follow them, and refer to them (Installed Autopilot123 in
accordance with AirplaneManufacturer drawing #123-456-789). You don't
have to pay a royalty, and pretty much any FSDO will accept that as
valid.

If it was approved on the type certificate, you don't even need a 337. Changes
in accordance with the aircraft specifications as certificated are not major
atlerations as far as far as part 43 is concerned.