Although this is a COE, the cab heater is installed and in the typical location (passenger side toe board).
The heater is not the triangular Harrison Heater posted in the CCKW section, but looks like a modified Chevrolet Deluxe heater. You can also see the heater supply and return.
Here is a Chevrolet Deluxe heater... some minor differences, knobs and trim being the biggest. I did flip the image to so it matched up the TM image... so the logo will be backwards.
The one question I have, and not addressed in any TM I have... did closed cab trucks have working defrosters????