I really like my Extreme Outback setup and I know they sell the bits seperate so you could contact them for what you need and any questions.
Mine sits on top of the rear of the roof rack and it works great regardless of dust, snow, rain or anything else.
Most folks mount theirs under the rig but I wanted mine up where I could show it for teaching purposes. I did plumb a quick disconnect hose fitting under the rear seat.
The hose from the compressor to the tank goes to the center bottom of the tank with a drain plug to get moisture get out if I am in a humid area (not often in arizona).
Then I added a quick disconnect to the tank and a line going to the rear seat disconnect.
Easy as can be.
cigar smoking, wilderness first responding, ham talking night nurse who is overland certified and a fellow of the Royal Geographical Society.....
now everyone say "so what where have you been lately?"