You probably can't find one for sale because the GMC's are fairly rare to begin with, and parts may be hoarded for that same reason. I know for my '46, finding GMC specific parts is not easy.

Whoever told you it was a Pontiac piece were probably only basing it on them looking similar. As far as I know there is no interchange on body parts from Pontiac to GMC.


1946 GMC Pickup - S-10 Frame, 455 Buick, TH400, original patina.

My 46 GMC on Photobucket