One late model heater setup that can workout well in the older vehicles is one from a late 70's or early 80's (not sure on years) Nissan truck or possibly an early 80's compact Dodge/ Mitsu. Arrow trucks.
My Dad is using a Nissan one in his '46 truck. Doesn't use all of that stupid plastic ductwork. Just a self contained unit. I think the dimensions are about 16" tall, by 12" wide, by 8" deep. Heat and defrost, not sure if they came with A/C or not. Local yards usually want $20-$35 for one.
