The good news (and bad news as far as pricing is concerned) is that parts for this generation truck can be more commonly found due to the popularity of the L'il Red Express trucks. For instance, the 1977 grill is the same as the 1978 L'il Red Express. I believe the only differences on the front were the color of the urn signal lenses some years.
You could probably get a decent deal on a driver-quality grill and leave the show-quality grills to the restorers.
Would you consider one from the same body style with a crossing pattern? The egg-crate pattern was acceptable to me on my '84, but the grille on the '86 to '90 models looked bolder, and it should fit without any adjustments. You might find one in a junkyard.