G'day,
The factory LHD under dash unit will fit in your RHD Troopie, but the Vintage Air one that goes all of the way across will not. As Mississipboy said, the 2F stuff will fit with a bit of playing around on the engine, and all of the switches, etc. will work as well.
I used an air con radiator that I ordered from an air con shop in Denver, and made the mounting brackets myself. The evaporator and lines were all put in by an aircon shop.
The only really specific item you will need that is for RHD only is the air duct which goes from the fan on the firewall to the factory heater unit. This has a 45 degree bend in it to allow the underdash unit to fit.
Marv used to have a number of air con units, and I would guess he still does. 818-882-1238. I know that there are some after-market air con units made here for RHD, but I'm not sure who makes them.
You may find that the air con is not sufficient for the size of the troopie (at least if it gets over about 90). When I was in Phoenix one summer with my troopie, I found that putting a clear plastic shower curtain behind the front seats worked really well to keep the cab nice and cool. I used one of those shower rods that has a spring in it to wedge it against the wall, and put it across the top of the roof above the rain gutter. Then the only part which was open was a small space above the rod.
I hope this helps.
Cheers,
Josh