My husband just heard from someone in Canada the other day (a mechanic) and he said that they are already starting to convert AC units to propane, especially on farm equipment.  He said that originally AC units were propane then went to R12 and that didn't work too well for the environment and then 134a, which also didn't work well on conversions, so now they're about ready to start using propane again.

  Sharon & Bob Mendonca
  88 Westy
  88 Vanagon GL