The installation manuals for the heater are here:
http://www.espar.com/documents/airtronic.pdf
A typical behind the driver's seat mounting of the heater looks like this:
I installed mine on top of an ammo can and mounted the ammo can to the floor of the cab. This allowed me more latitude in routing the air inlet, exhaust and wiring cable through the floor.
These are usually a diesel/kerosene heater. Thus a secondary fuel tank is needed. A typical LinDen Engineering auxilary heater tank looks like this:
This extra tank has confused more than a few people.
-Evan