My newly purchased truck. A 80 model d100
Has no ac. It’s 103 today and as I’m sweating my ass off I’m curious who has used an underdash
Unit in the truck. If and what type. Has it performed well?
Because I love my truck but I’m begging for ac now

An under dash add on system should have no problem cooling that truck.

Only experience was an '83 Ram with dealer add on A/C. FAR superior cooling to the factory units of the era.

Old school linky 15,000 BTU and 290 CFM should be fine with your truck.

https://www.oldairproducts.com/

Old Air Products
1201 Forum Way South
Fort Worth, TX 76140


Hurricane
IP-400HCDE - Inside Package, A/C Heat and Defrost Unit
Underdash A/C Heat and Defrost Unit, Slimline (coil right, Electronic Heater Valve)
$550.00

i can't add truck experience, but did two universal application, e-bag cheapies, that worked very well.
one on a 64 ford galaxie 500, and another on a 58 chebby impala.
these kits contained cut to length hoses, a bunch of assorted fittings in different angles, polished new style compressor, dryer, etc, as well as the under dash evaporator and control unit.
these have been in service for 5 or 6 years with absolutely no problems, and cool these cars great, putting out 40 degree air temperature.
i can't tell you how many btu's these kits put out, however.
you also have to make mounting brackets for the compressor to fit your engine. that was a simple procedure here.
if you have some fab skills, it shouldn't be too hard of an addition to add to your truck.
just my experience. your mileage will vary.

I converted my '71 (Sweptline) 318 and the wife's '79 LRE to the modern Sanden compressor since the intake I used on both wouldn't work with the factory RV2 monster. I found a newer model of the same engine (for each one) with the Sanden and striped the entire front of brackets, pulleys, bolts, etc. Easy bolt-up with a brand new compressor and had new lines made. If you can buy the under-dash unit by itself, junkyard bracket set, and pick up a compressor/condensor/dryer/most hoses from Rock Auto, you can do the job without laying out a ton of cash.