68 had its own dash, the key switch was in the dash, its on the steering column on latter cars.
68 SS Chevy II's had "super sport" in block letters low on the front fenders, all others had "SS" higher on the front fenders. 68 Novas had the "Nova" nameplate on the rear quqrter panels, 69 and later cars had these moved to the front fenders.
68's had a three spoke steering wheel, 69 and 70 had two spokes and a four spoke wheel was used in 71 and 72 but I dont know if it was across the board in all of them.
68 and early 69 small block cars had 327 engines switching to 350's sometime in 69.
Bumpers become flatter in 70. Notice the larger parking lights in the newer bumpers.
68 had almost square side marker lamps, the front ones on V8 cars included the engine size call out in the front lights. 69 had small erctangle marker lights, 70 and up had larger rectangle side marker lights.
Taillamps got bigger in 70.