Installing A/C in a 1988 Ford F-150?

I paid a visit to my uncle the other day and the conversation somehow shifted to his truck. Summer is upon us and living in Arizona without A/C is no joke, so I thought I d ask if his was working fine. He said his truck didn't come with A/C out of the factory, something that I found quite odd but a look under the hood confirmed this. There's no compressor nor A/C lines at all. He does have a climate control unit on the interior and with it is a cold and hot temperature slider. Is it possible to maybe add the A/C components and make it work? Don't know much about trucks but he has a 1988 Ford F-150, 6 cylinder engine, dual gas tank, 4 or 5 speed manual transmission, I'm not sure since shifter knob doesn't have 5th but a "D" in its place. I took interest in this because I found it to be quite odd but mainly because it is his only car and daily driver and does have 2 kids that often ride with him. Just last week we reached 117 degrees here in Phoenix and I don't think it's very safe. Any help is greatly appreciated.

Check out Ebay someone out there's offering to fit ac retrospectively and probably much cheaper than a dealer.

HI, there are many cars/trucks sold with out A/C… All temp slider controls have a Cold to Hot setting. That just lets the driver chose how much heat he wants to add to the air coming out. If it has no A/C. Are you sure its not a OD (OD= overdrive some 5th gears were marked with OD) not just a D.
A/C can be added to any car/truck. But well need its own controls if there's no switch that says A/C on the dash.