Did GM use a flat six around 49?

I was looking at a 49 ish chevy truck in a wrecking yard recently that had a flathead straight 6 in it. This isn't the first one either. I have also seen a GMC before of about the same year with a similar motor. I've been told these trucks didn't have any flat head sixes so I'm puzzled. Sorry, no pics.

Even more odd was that the old Chevy had a "Chrysler Airtemp" logo on the drivers door like it was some sort of service truck. What was "Chrysler Airtemp" anyway? An HVAC division?

 

airtemp was the a/c division of Chrysler, I think...I know our 67 plymouth with factory air had an airtemp sticker on the window.

GMCs used Pontiac straight 6s in the 30s, iirc.

Pictures help a lot in identifying engines.

 

Pontiac and Olds had flat 6's....Pontiac 'till '54...Olds til '48, I believe...

 

I know they used 230ci Olds flathead motors, but I dont know til when.

 

Are you absolutely sure it was in fact a Chevy truck? Plymouth made a truck in the mid-40s that bears a striking resemblance to the Chevy trucks of the same era (the art-deco jukebox ones). It might have been a Plymouth...