One of the first ones I ever did was modify my first 2035 that I bought in 2017 getting back into the hobby from a small shop (Schultz's) in Dayton Ohio and in 2018 updated it to ERR AC commander in the tender and railsounds using an MTH tether harness. I even wired the original coil coupler to TMCC rather than shoe.
Chuff annoyed me in trying to get a good trigger (I did not like tender axle driven) and eventually my solution was drill the backside of the front fireman side powdered metal driving wheel and insert a tiny magnet with superglue. It lined up to a matching hole in the aluminum frame of the motor where I also superglued a Hall Effect sensor.
My other AC commander install was into an early FM Trainmaster 2321 also with Railsounds. Someone left the orginal horn D cell battery so the holder and frame took some corrosion.
Another one I did was the FARR Great Northern- again, using an MTH 10 pin tether wiring for a simple plug in system.
