Re: GMC Shutter Grill
You might send a PM to Camo Monster - he has a louvered grill. I have seen these on Mack dump trucks pop open and closed going down the road probably based on radiator temperature. They would be activated by some kind of servo driven by air, hydraulic fluid or electricity.
If working, these are handier than a "weather front." That is a square piece of canvas that goes over the grille openings. They are installed for winter driving using permanently installed snaps like a boat cover. The weather fronts usually have a zipper in the middle. The zipper can be pulled partway down to let cooling air in through a "vee" opening at the top. But you have to get out in the cold to adjust the size of the opening.
I used to see weather fronts on all the old International flat front hoods. But come to think of it, I can't positively say I have seen one in a while, but I can kind of picture newer ones. I would definitely grab a set of power louvers instead if I thought they would fit on a bus I bought.
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.