<Vintage Air makes several heat, defrost and A/C units mostly designed for
the hot rod market.  All functions are <combined into one unit heater AC
evaporator and fan unit.  Using one of these would allow use of only one
fan <and one ducting system.

I have also been thinking of this type of setup for my former diesel van.
I was thinking you could use a small flapper box, like on small aircraft,
to either have fresh or recirculated air enter the Vintage Air unit.  On
the aircraft they are used to either let fresh or heated air from the heat
boxes enter the cabin.  Since my fan died a smokey death last week, maybe I
will start thinking about actually doing this while I'm in there.

Dave K.