I don't think I'd go with a straight stock '50's type A/C system. With the cost and availability of R-12, it's definitely worthwhile to adjust for using R-134a. The basic differences are in the condensor (which any of the above companies can size for the car) and the fittings used to charge the system.

The big difference is the interior appearance. Universal units mount on the trans floor and can take up quite a bit of space. The newer systems from Vintage Air, Hot Rod Air, etc., will usually fit behind the dash without problems. The only issue is vent placement and control placement.

I'm installing my center dash vents and the A/C control unit in the dash where the radio was. I'm putting the radio and navigation system in the console. The outside vents will be in the outside kick panels just below the dash. The system looks symetrical and without an 'add-on' look to it.