Denny,
Three out five of my trucks came with the "deluxe" (actually an air-flow or outside-air) heater. These were available from 1947-55 (Chevrolet trucks and GMCs) with slightly different housings in 54/55 but the same core.
The less expensive heater was the recirculating heater (round core) that did not change from 48-55 (Chevrolet trucks and maybe GMCs).
outside-air & recirculating heaters In 1947,
the first A-D trucks also had a deluxe heater , but I think this was only available in 1947. This heater had two motors/fans, one for normal heating of the cab and one for defrosting the windshield.
Here is the 1947 fresh-air heater. Denny, I agree with you that there would be a market for the round-cores and the air-flow rectangular-cores. The round-core style is more common but the air-flow type is not at all rare.
Of course, you could have any of your old/bad cores
refuilt by Chevs of the 40s for $375. Bet a "good radiator shop" could beat that price - if anyone finds that good radiator shop, let us know.
Tim
