There is a quality aftermarket AC company in my complex here at work in Fort Worth. The company is CC Classic and they do really good work. I went through the shop today and the owner showed me several of the vehicles he's working on now ('63 Thunderbird and '68 Ford Pickup).
The owner has a '80 SWB that is in great condition. He installed the AC system for our trucks in his and it is very clean installation. His truck did not originally have AC and the system he installed will cost you around $1800 installed. However, he sells the system for $1150 and it comes with awesome step-by-step instructions with detailed pictures.
The system uses the original heater contol so this system enables you to keep the stock look. He adds the two driver side vents and the two passenger side vents. The entire heater box assembly is removed and replaced with his components. He adds all the appropriate components under the hood with factory-like brackets and hard tubing. His truck has a highly-modified inline 6 with this system in it but he said he has all the necessary brackets to make it work for any engine setup. The beauty of this system is that it doesn't take up alot of space under the hood. All the components that are on the passenger side of the fire wall are not present. All you have there with this system are 3 or 4 pipes running through the firewall and under the dash. I think he will also take a truck that has ac and convert it to his system. Therefore, you will get back alot of that space under the hood!
Oh, and by the way if you mention my name (Scott Shelbourne), the owner will give me a kick back of $50.
See pictures here.
http://www.shelbournes.net/trucksite/CCClassic.htm
The company info is:
CC Classics Air Conditioning
2673 Gravel Dr.
Bldg 1
Fort Worth, TX 76118
817-284-5811
mds2660@msn.com