The idea will be to place it in the rear of the bus under the Z-bed. It will take up some space, but I'd rather have heat then an extra cubic foot of space.
I will also need to creat some kind of mounting system. I am thinking about removing the orginal vent tube to route my heater lines through so I don't have to cut or drill holes in the floor.
The next step is to figure out placement of the A/C cooler. I am considering two options: one is to mount the A/C cooler under the radiator so the airflow and dual electric fans can be used on both the A/C cooler and the radiator. I don't know exactly how much protrusion this will create under the bus. Once I start mocking up the air duct system for the radiator, I will take some measurements and make a decision.
Option #2 is to mount the Subaru A/C cooler on the outside of the framerail between the rocker panel (where the propane tank usually sits).
The only problem with this approach is that it will require additional fans, relays, and wiring to the underside. And since I don't have the additional fans, I am not sure how far down the whole system would sit below the rocker panel... Mounting the A/C cooler under the radiator would prevent the need for that extra work.