My '86 420 SEL was converted by the PO; although it does cool; it is not sufficient; I need some cold air hee in the South, and I don't like making excuses for the poor performance of the AC in a Mercedes-Benz S-Class, so I am converting mine back to R-12. I need a new compressor, anyway, as the seal on mine (noticed it's a rebuilt Nippondenso) leaks.
What is involved in comverting back?

By the way: I understand some of the refrigerant substitutes are propane or other similar hydrocarbons. What in the world happens when the evaporator ruptures while you are driving? What about a slow leak which might allow the substance to settle in a low place in the passenger compartment (like under the seat, where the seat-positioning electrics are located), or under the hood? I feel the flammable substitutes, although great refrigerants, are dangerous. A local attorney has photos in his office: he got rich when a client came in, who was burned when the window unit in an apartment blew flames out the vent; it had been charged with propane.