Is that a GS hardtop ?
In any case the top issue is rust. As in, none if possible. After that the hard to find stuff should be in good condition - grill, headlight buckets, taillights, rear center emblem, etc. Replacing those things can be very costly. Numbers matching driveline is a plus, but not absolutely essential. Rebuilding a nailhead engine is pricey so mske sure its in good shape.
Other than that its just the usual stuff when looking for an older car.
Just my thoughts. Sure others have good advice also.
Dan
