There are a few other differences too:
Headliner, Hood latch, Headlight benzels(black for 69), Bucket seats, Steering wheels and columns, Windsheld posts, door opening vents on 69, front fenders have different locations for side markers, rear deck chrome moldings, the arm rests for 68 have a chrome strip in them and 69 doesn't, The rear arm rest ashtrays for 68 have ribs in them and 69 doesn't. Wiring harnesses are different, The door panels are different for the doors, but the rear panels will fit either(just depends on the design--69 has a different pattern than 68)and I think thats it for the differences.
The similarites: there is a lot that will fit either. The interior you take one and make fit in the other.