The one pictured looks more like a 530i one, not a 528i one, which is better and has a much larger aux fan mounted on it. The 528i one has flat tubes, not round, and is a serpentine design. A much better condenser IMHO. The Aux fan mounted in front is critical too, and while it looks the same as other BMW ones, it's not, it's got a peculiar shape to it to fit in the space. This place
http://www.ackits.com/c/Parallel/Parall ... minum.html seems to have a pretty good reputation for parts, but probably won't have OE replacement anymore. Their parallel flow condensers are supposedly quite good, but I haven't used one myself.
Good A/C is all about exchaging heat, and size and design both play a part. As I mentioned earlier, the Aux fan is critical too, if you ever see a 528i one next to a 530i one, the difference is substantial. And you need a good fan out in front to move air to exchange that heat. IMHO, OE parts work pretty damn well, at least with R12, and it would be easiest by far to do. Some or many of the parts are probably NLA, so a doner car might be the way to go, but you can mix and match parts too as long as they fit. But if you do go OE with doner parts, expect to have to rebuild the high pressure hoses if they are the red type, they become porus with age.
