Okay. This is really very straightforward.
An air conditioning system consists of an evaporator, a condenser, a compressor, an expansion valve and a dryer. Older systems ran R-12, which was more efficient (read smaller evaporators and condensers.) Modern systems run R-134a, which is less harmful to the ozone layer. They're every bit as effective as an R-12 system; they simply need a larger condenser (that thingie in front of the radiator).
If you want the look of a vintage system, run the head unit - the piece inside the interior. The most important differences between an R-12 and an R-134a system are the compressor (different elastomers for the seals) and the condenser (it has to be larger to compensate for the reduced efficiency of the refrigerant). These are all common components. The compressor mentioned earlier is a Sanden unit - not a Sandeen. It's a standard swash plate design adapted to many installations; its modularity is what makes it an attractive alternate for vintage air applications.
None of this is cheap. To have a functional A/C system in an older car is going to cost you five figures - any way you cut it. There are no shortcuts, as there has to be a compressor and condenser change to make it happen. If you can find someone with a stash of R-12 (and yes, it does exist) the bill will still be within 80% of the cost of converting to R134a. Irrespective of what path you take, you're still north of a grand to get an A/C system going.