hey is it a chopped down vitara or windowless coz otherwise thats a pretty massive heater to be running in an enclosed truck 24/7
personaly if I was doing one I'd look at steel tube through any parts it had to travel through the cab (insulated/ducted/screened whatever) if you cant run anything underneath and I'd put some pretty good thought into the radiator location to keep it well back or screened from the seats and cab area coz boiling water can cause 3rd degree burns and serious injury if something goes wrong