I’ve never seen a GMC look like that yellow sedan delivery, which has “Pontiac” written all over it. But then I’ve never heard of a Pontiac sedan deliver in 1958 either. Once again, we’ve just entered the automotive Twilight Zone: Canada.
Pontiac’s last US market sedan delivery was in 1953, but north of the border, Pontiac was of course an alter-identity Chevrolet, so there was a sedan delivery. And since GMC trucks was teamed with Pontiac in Canada, it made sense for it to be marketed as such, even if it did say “Pontiac” across the front of its hood. And of course there was a Chevy six under the hood.