You dont mention what model car you have , but assuming its an older one that never came with ac , , Get ahold of Jon at www.nostalgicairparts.com ( or look aroud the site first at add on evaporator kits for under dash or in dash kits ) I do a LOT of custom AC work and have delt with these folks for years. You can easily get brackets to fit a Sanden style 709 compressor onto most brick engines and the rest depends on how complicated you want to get and how neat you want it to be. If you just want cold and arent too concernened about looks and have the room, the one piece underdash units make things simple. The ducted units are more complicated, but they can be mounted anywhere including a trunk ( which also gives you the option of adding rear passenger vents:-) you run the front vent ducts up under the floor on in the headliner. Ducted units can be sheet metal boxed in the engine compartment as well.
if it is a newer one , you would likely be better grabbing new replacement parts and building a system, but dont get used compressors, evaporators or condensors. I cannot count the number of times folks have brought me vehicle that they have pieced together systems from jusnkyards and came to masaying all they needed was hoses made up and a evac and charge and as I start shaking my head no, they dont understand, but once we start the all day long process of removing those parts and flushing the rusty crud out and adding line filters ( for which I tell them I'm not promising anything ), they start to get the picture. You can get a NEW compressor for less than a rebuilt one or even used in some cases. Cheaping out on this will cost you in the long run
The only thing even remotely safe to get used is switches brackets and lines, ,make sure they come off something that is freshly unsealed and flush them out GOOD
--
-------Robert,:'00 XC70. '95 960, '93 940t, '90 240 wagon, '94 940SE, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually