What is this Heater it is from the 1951 Chevy Accessories Installation Manual it does not look like the round recirculating type.
It has more of a square box. Is this the same Heater
The article states it is a 1947-48 GM recirculator heater.

Recirculating type looks like the 1st two pictures in this THREAD.
It has more of a rounded box with a round heater core.

I thought General Motors offered from 47-55 1st series truck
A rounded box recirculating type heater with a round heater core.
And a fresh air/air flow HEATER semi-round box with a rectangular heater core.

Was there more than 2 types of heaters offered By GM?

1954 Chevrolet 3105 Deluxe Panel Truck
w/Factory HYDRA-MATIC