I'm also not at all convinced a dash unit will cool a 'burb. I base that on what the factory heater does in my '62. Or doesn't do, as the case may be.
It's a long way to go, but one idea I had for A/C would be to run some custom vents along the trans tunnel and have them come out under the seat, blowing back to the passenger seat. I'm planning on building a custom center console in my truck, based on a factory high-hump trans tunnel. My '62 Sub came with a factory granny 4spd trans, with the high hump. I'm replacing it with a factory low-hump trans tunnel, and will be cutting/welding the factory high-hump cover to have cup holders, a small storage "dish" like today's center consoles, and a factory cigarette lighter to use as a phone charger. In my situation, I could run heat or air ducts under the console and have them extend under the front bench seat, exiting under it in the center, and install vents to direct the air, much like a modern SUV.
I'm not going to run A/C though...even in Atlanta during a record hot summer, it wasn't unbearable with the windows open, the vent windows open and the kick panel vents open. If it's 95 and below, as long as I'm rolling just a little bit, I have a cool breeze. 95 and above, it's a warm breeze, but still enough to keep me from sweating.
As for the headliner, I've got the same issue. I installed Dynamat in the ceiling. Next, I'm going to get some 1/8- or 1/4-inch MDF, cut it to the same shape as the original headliner inserts, hit it with spray upholstery adhesive, and glue some sort of fabric to it. Then I'll reinstall as the originals were put in. That would work for a fairly factory look.
Right now, I'm leaning towards doing something just slightly different, and rather than cut individual panels, I'd make it one long piece (fabric-covered MDF), screwed to the roof braces so it was a continuous headliner. The edges would be tucked into the side interior trim pieces that run the full length of the body. Then I'd either use finished-looking screws with recessed washers like are found on the door panels of cars, or I'd make a simple headliner bow out of flat stock or sheetmetal, like the chromed headliner trim pieces in '58 Buicks and Impalas.
-Brad
