Was up over the weekend and did some more looking around. I'm going to guess this setup is pretty common across the different designs:
The heater core is at the bottom, a valve controls the amount of water that is let in it seems. It leaks a good amount, it seems to come from the valve body.
The airbox has a fan and flap at the back (left in the picture) that controls heat to the "passengers". There is flap on the right that lets fresh air in from the outside.
Heated air is sort of free to circulate in most of that box, with one close space fed by the fan on the left, directed at the driver (or the passenger, depending on the flap setting).
In the top right is the fan that seems to feed the window defroster:
It pulls warm air out of the box and pushes it in there. Both fans have this thingie attached:
I'm guessing it's some sort of high temp disconnect? Or a current limiter, or .. Really thick coils. Heavy gauge wire going to it.
My thinking now is:
- Rip out the bottom heat exchanger and fan (on the left)
- Run new heating lines with no shutoffs in the cabin (just use the ones in the engine compartment
- Get a 28k BTU JEGS heater + duct kit. One nozzle aimed at the driver. One feeding the existing window defroster
- Reclaim a lot of the space there, and reduce the risk of leaks