My 94 D90 NAS came with the original 94 AC unit but after living with it for over a year I decided to replace it. The AC unit worked but there were a few things I didn’t like about it. 1) the design is horrible in that it takes up a large amount of the passenger footwell 2) the controls are located in the center dash which mean you can not mount any of the stereo or switch panels in the center dash 3) my unit was missing the front facia in the passenger footwell which meant it exposed some wire and tubing 4) it had a leak which meant it had to be charged regularly to keep cold.
Rovers North makes a replacement unit that is more efficient, smaller, with the controls built into the unit. Not only does it work much better but it cleans up the center dash and the passenger gets more leg room. Its not a cheap replacement at $4k plus about $2k worth of labor….but if you plan on driving your truck regularly, AC is nice to have since there is zero heat insulation from the engine.