I have seen several old Classic Buicks modified with a/c setups. Does look pretty involved. For best response, I'd recommend you to post your question on the Buick Club of America site, hosted by the AACA.

In my opinion, it isn't worth the hassle. You will pretty much need to take the whole car apart if it isn't already. You've got to change the radiator...alternator...engines pulleys...heater core assembly...and the list goes on. Plus it never really seems to work 100%