[elhigh]

The point of closing your grille, even in an older ride like yours that doesn't have such effective streamlining, is to eliminate the drag of air getting in and then having to get it back out from around the engine. With most/all of your grille blocked you'll create a sort of nose cone of high-pressure air in front of you as you drive, not as effective as an actual nose cone but still better than nothing, and that will direct more air around your car.

If you spend a lot of time in stop-and-go or at slow speeds, you'll want to leave more of your grille open until you've had more opportunity to monitor engine and underhood temperatures. Switching to an electric fan will eliminate a big drag on the engine while you're cruising; to the best of my knowledge virtually no vehicle needs the belt driven fan while at speed.

I bet you have a big opportunity under the car, too. Lots of potential for belly pans down there on older rides.