I had a couple of them myself. Never will forgive Ralph nader for killing them.
They are great in the snow, especially if ya throw a cement block in the trunk up front.
I also would put it up for the winter though...it's too nice to trash. Find a "winter rat" and save the Corvair.
AS for the heater......as I recall, the heater box wrapped around the exhaust manifold. If you had a mild exhaust leak, the fumes would get pumped right inside the car thru the vents under the back seat. Keep that in mind.
If it's not heating, maybe the heater box is trashed (no water to heat in this one). Maybe someone worked on it and decided to remove the box or the fan is just trashed.