For your era truck: the factory shocks were heavier duty, had a cheap aluminum skid plate covering the front differential, and one covering the transfer-case. Claim of a heavier duty air filter, and the stickers on the bed.
The G80 locking rear differential was still a seperate option from the Z71 option.
You will not notice a difference in the ride quality of the truck. Suspension spring rates can differ between two identical trucks (both w/ Z71 package), so you cannot say that the Z71 package includes heavier rated springs; because it doesn't!
My uncle had a truck just like mine; the only differences were the last few digits of the vin (build #). Both '97 ex cab short bed, same motor, tranny rearend gears, color, 3rd door, ect. The difference was his has capitan's seats, mine has 60/40 front, and his had the factory tow package included, mine did not... BUT mine had one more rear leaf spring than his did! Never did find out why.