I just spent the entire weekend installing the heater / defroster system in Bussy! I don't have the ducting permanent yet, but everything else is pretty much "there." I used a Flex-a-Lite Mojave heater, added a custom made plenum and ducted into the standard bus toe-warmer / defroster fixture up front. The heater is between the seats enclosed in my 'console.' There will be a permanent duct running above the floor to the front. I considered running it below the floor, but since I have no passenger seat (my pantry is built there) and there are all sorts of other things like radiator piping below the floor, I think this will work out fine.
I just tested it and that alone is worth putting the Subaru motor in for! The heater piping is the thermostat bypass on these engines. That means that before the thermostat opens, you have heat in the cab and defrosters that actually work! I have a valve for the amount of bypass (the heater flow is restrictive so my bypass valve never totally closes) and when I move it to "full hot" the air coming out of the defroster is too hot to hold your hand in for very long! I also have a valve to select recirculating or outside air. As of now I'm planning on hooking the controls up to the stock bus heater controls - have them all trimmed and positioned but haven't attached the fittings yet.
Soon I will re-install the Espar diesel heater but it will be primarily for camping / snow outings and such times when I want heat when parked. I do have the option at this point of ducting it in along with the Mojave, but I suspect I will duct it to the living room instead.
-- Dave "Busahaulic" Pearson Fall City, Washington Remove obvious from addy to e-mail