Rocky Mountain Avionics (Mitch) and I have done business for over twenty years. There are two great avionics shops in Montana. I use Mitch exclusively.
Even though I only have a little Cessna 150 the guys at Rocky Mountain Aircraft treated my as if I had a big jet. Courteous professional service and gave my 1965 150 a complete avionics upgrade that works great. My plane is now IFR certified with Garmin GPS avionics.