I wouldn't have A/C on my muscle car, except, has anyone tried the $89 portable 12V. A/C unit? You fill it with water/ice and it lasts 8 hours. Does it work?
Blaux portable ac air cooler is one marketer. I see several outfits sell them. Reviews (and Blaux) say its not a/c but it helps and will lower temp 10-15 degrees and cut humidity. Its an ice hog so you don't wanna have to buy ice. Its a cooler that holds a few bags/blocks of ice. Reviews aren't disappointed
The old Swamp cooler. Hard to believe that melting ice and water wouldn't make humidity. One thing A/C does well is remove humidity. 80° at 40% is quite comfortable. 80° at 80% isn't so much!