hi, the hungarian importer has quit doing the business, so i'm not sure whether there is an "official" garage service here. however, you may start this by looking at the engine compartment , to see if it is possible to fit the compressor, and if there is enough space for the longer belt. if it is, the hardest problem is solved.
you can fit the condenser almost anywhere (most cars i've seen had enough room for it, even originally non-AC equipped models).
as i heard, the most often used radiator is originally Suzuki part, that fits in relatively small spaces. if you can buy teflon tubes, there should be no problem to prepare them for the desired length.
if i were you, and it seemed that there is enough space for the AC parts - and the installation is possible, i'd manage to drive the the compressor separately from the water pump and the generator. this may be a relatively easy step considering other difficulties.
keep in mind that this whole thing may cost a fortune... you wrote that you are about to became an owner of a classic. that may be easier to install an AC into that car any you would surely have more fun:)