I have a 1970 R/T that was non air. Here I was around 1984, on a hot Summer day in St. Louis, sitting at a stop light with a 440-4sp. thinking that I had the best car on the road. Next thing I know, a '72 Cuda is coming from the other direction, making a left turn right in front of me. We check out each others cars: They notice mine looks good (I hope), I notice they had their windows up. It's hard to look cool cruising with a towel in your hand to wipe off the sweat.
I found a complete A/C car in the junk yard and pulled the air box, then traced all of the holes onto a piece of cardboard. I then lined it up on my firewall and drilled and sabersawed all of the holes to bolt it in. The only thing on the firewall missing is the lip that goes all the way around the heater motor. I then spent the next few years getting a complete dash assembly (with ducts and A/C control) , finally finding all of the brackets on a 440 wagon, then finally finding the correct hose that connects the compressor vacuum side to the firewall on a big block 72 Roadrunner.
It can be done and it looks FACTORY.
I still have the car that I bought in 1980.
Here is a link to a pic, Just ignore the other Fast and Furious toys that I built, I did it for the money.
Oh, the tilt column from a Cordoba that I modified looks FACTORY too!
www.issisolutions.com/cars.htm