I got the setup for my 53 Chevy here: http://www.rainbowproductsonline.com/

The evaporator I got was compact and fit easily behind my dash. As for the brackets for my old straight six. I just patterened those using some old balsa wood and then went to a local machine shop to have the brackets made from steel.
It took me a weekend to get everything going.

If you are looking to save cash, head down to your local junkyard and try to find a car with the same size motor as yours. Then you can pull everything off. That is what I did years ago on a 1970 Oldsmobile Delta 88.