Heaters were a dealer option in may of the early trucks, wagons, sedan deliveries, etc.

The '48 truck originally came from Mississippi and had a heater about the size of a coffee can. It wasn't much heater in Tennessee and it definitely had to get replaced once I got to Indiana. The replacement seems to be a more common heater for trucks - I've seen a couple of them in other restored vehicles.

Even the 1950 Dodge Wayfarer had an anemic add-on heater.