There's a bunch of parts that are hard to find...
or expensive if you do find them. Top latches and top straps come to mind.
It's been years since I've seen a fusebox cover (not the plastic cover that immediately covers the fuses, but the larger one that's the same material as the dash).
There is an under-body tunnel piece that directs air from the lower grille into the central tunnel, very hard to come by.
A good windshield would be a great find. The emergency brake surround in good shape would be a keeper too.
Plus any aftermarket parts like double bubble tops, euro bumpers, Montecarlo headlights, etc.
That's a "starter" list, anyway...
Pete