Despite its appearance now, I actually used the Purple Pig as my daily driver when I first moved to California, commuting 70 miles a day. With nothing more than a seat inside the car, and temperatures where I lived at the time too much for me to bear on my afternoon drive home, I realized for the first time why installing air conditioning was so popular in hot rods and customs! Bear in mind I'd just moved from a country where heaters and demisters are requirements, not cold air!
Four years on, and I couldn't imagine not having A/C, so I called Vintage Air to discuss my requirements for the project '49. They sent me a couple of mock-up evaporator units to try under my dash, which enabled me to determine which one would work best, and to drill the mounting holes in the firewall before I welded, filled, and painted it. Once I'd determined the Magnum Gen IV evaporator was going to fit, and indeed fit better than the smaller Compact Gen II version (the shape of the Magnum fit around the sheetmetal under my dash better and allowed the evaporator to sit higher on the firewall), Vintage Air sent all the components I needed.
I ran across a small problem with the location, but that was my fault. I wanted to run the hoses through the firewall, as I thought I could use the stock fresh air tube hole, and proceeded to weld and paint the firewall. May I suggest you fit your A/C system in, then, and only then, start bodywork!
Despite the modern underpinnings and running gear, I am very keen to maintain a vintage look to the interior and exterior of the Chevy (yes I know the evaporator hangs below the dash, but I'll disguise it as best I can later) and as such didn't really want modern A/C controls to show. I could have hidden them in what's left of my glovebox, but I'd rather have them easily accessible. Vintage Air offers conversion kits for owners of some vehicles to retain their stock heater and A/C controls, and their '61-62 Impala kit converts a three-cable system to electric operation. With the '49 Chevy using three cables, I used this kit to convert my stock controls.
If I've connected the cable converters correctly, my TEMP button should now be the thermostat lever, controlling the temperature from hot to cold, the AIR button should control the blower speed from off to high, and the DEF button should be the mode lever, controlling mode positions from dash to floor to defrost. A combination of positions offered by the three levers will provide heat or cold air to the various vents, the sequences shown in the Vintage Air conversion kit instructions. Also shown in the instructions is the calibration procedure, which I haven't done yet because the system needs to be completely hooked up to do so. This will set the range of travel for the cable converters connected to my stock control panel, setting their highest and lowest points.
 |  Vintage Air has these great...  Vintage Air has these great mock-up evaporator units that enable you to see which one will fit your project, so you can purchase the correct one the first time. You can check with one of their dealers or go to Vintage Air directly, and for a deposit of around $50 they will send you one of these units. When you return it you get the $50 back toward the unit you buy that you now know will fit. These are the Magnum Gen IV (top) and Compact Gen II units. |  Don't think the smaller the...  Don't think the smaller the unit, the easier it'll be to fit. I actually couldn't get the Compact evaporator up under my dash, owing to the large recess to clear the head on the stock straight-six. The Magnum Gen IV is shaped to clear such a protuberance, though I did have to trim 3/4 inch from the lower lip of my dash, as shown. |
 Here's the Magnum Gen IV mock-up...  Here's the Magnum Gen IV mock-up unit in place. Guess I'll be saying goodbye to the stock glovebox hinges. There's probably another inch of room to move the unit up, but I'll need space to get my hands up there to connect the defroster vents as well as clearance for the wiper mechanisms to operate. |  With the mock-up unit still...  With the mock-up unit still in place, and before I filled and painted the firewall, I decided to mount the bulkhead fitting on a plate over the old fresh air vent hole. There was enough room behind it to install the fittings and I figured the removable plate would make access easier in the future. |  Here are the contents of one...  Here are the contents of one of the three boxes that arrived from Vintage Air: the GEN-IV system, including the Magnum heat, cool and defrost model evaporator and mounting brackets, compressor, electric solenoid heater control valve, ducting, fittings, and wiring harness. I won't be using the demister vents, as the stock ones will suffice. The box also contained the Pro-line compressor and alternator bracketry I'd requested, since I'll run V-belts rather than a serpentine system. |
 Looking through the glovebox...  Looking through the glovebox opening, you'll see that the front mounting bracket needs modification. The brackets are not application-specific. |  Now with the actual A/C unit...  Now with the actual A/C unit in place, I marked the bracket inline with the upper glovebox opening lip and bent it forward, slightly less than 90 degrees to line up with the lip. |  I welded extra steel to the...  I welded extra steel to the bracket, leaving a cutout for the glovebox latch, and bolted the bracket to the lip. I left the original mounting holes in the bracket as they'll likely be useful to zip-tie the defroster ducting to, in order to keep it away from the wiper mechanism. The wiring you can see comes from the A/C controls. |