The non ac housing won't fit, I guess I could spend the 170 for an ac delete box but I didn't want to.
To answer your question:Yes, on muggy nights just after a rain, late nights in the fall or early in the morning the inside of the windshield will fog up. Now on to new business.
Why do you say "it won't fit"? You'll need a small piece of metal (4"x6"?) to cover the hole inboard of the non A/C box but other than that, it's a unbolt & install deal.
I've converted a couple trucks to A/C...same deal only you need to cut the hole a bit bigger & drill some bolt holes.
As mentioned, your other option is an aftermarket underdash unit. I do think with some planing & fabing, a blower could be moved inside some way on the plenum since nothing is outside in the box, but the blower.
I'm not real sure just "how cool" it is having all that bare area really is...to each his own. Lorne