A couple other items to note:
1 - The rear window looks to be tinted. It is not supposed to be tinted.
2 - There appear to be stereo speakers mounted on the back wall of the interior behind the seats and rear compartment. Those obviously are not original either.
3 - Based on how the glove box door fits, and how the cover below the steering column fits, my guess is the dash was replaced. It's probably your typical after market dash.
4 - The owners manual pictured 3 pictures from the bottom is not original for a 78 Pace Car. That owners manual is for a 78 Corvette 25th anniversary car. The original 78 Pace Car owners manuals look like the original one I have pictured below.
What the VIN # of the car? Whats the Trim tag info? 22K miles? And NOM? For the same roughly $25,000 USD I think you might be able to get a nicer more original 78 Pace Car. Just my two cents.
-Dave