I have a 55.1 with the GMC dash. I used a system from Old Air Products. They worked with me to piece together a system. The normal unit fit under the dash, but I had to build a shortened glove box insert, about 3" deep. I mounted the controls in the ash tray hole. I put a single vent under the middle of the dash and a ball vent in each corner. I reworked the ebrake rod to move the release knob over to the right a few inches. It works well but the vents are mounted low and so I don't get air in the face. This makes it seem to cool more slowly. I should (and may) swap the center vent and put the vent in the ash tray hole and the controls under the dash.
regards,
Leon
