Wow this is a older post.
Truck engines didn't change for a couple more years as I recall and I also have seen '78 Vettes with factory engines that were Orange so they must have held out a little longer as well. Maybe becuase the trucks and Vettes didn't get "corporate engines". On some models back then you didn't know what the heck it was going to have under the hood, Chevy, Olds, Pontiac or Buick. Quite a few B-O-P new car buyers tried to sue GM for fraud when they found out their new Buick, Olds or Pontiac had a Chevy engine under the hood.
Well in Canada all the Pontiac's have almost always had a Chevy under the hood. I was looking a buying a 66 Pontiac full size car and it had a Chevy 327 under the hood. After a little research on it I found out that in Canada all the Pontiac's had Chevy power plants because of some legal reason. Can't remember it right now. But yeah the Canadian Pontiac's came with Chevy's ( think that the firebird came with a Pontiac power plant). Just thought you would like to know.