I removed the under seat heater from our '41 Pontiac sedan to restore it.

Under the seat? Is the heat source electric or is it plumbed with engine coolant?

If it is like Studebaker it plumed into the cooling system. I bet they use the same or very similar parts.

I know that tri-five Buicks also had these. Probably very similar. Might be a source for parts.

Will Willis