The car at Best of Show Automotive has got to be the same car that was featured in the 9-1987 issue of Muscle Car Review in my opinion.
I have attached nice clear scans of both pages. The car was also shown at the GS Nats in the early 90s and I have photos of it, but they are not here at my house, I'll get them next week when I visit my Dad and scan them in if there is any doubt.
Why do I think it's the same car? Well in 1972 there were 7,723 GS Buicks made (this includes includes GS 350, GS 455, and GS Stage 1). Of the 7,723 only 113 were painted Regal Black. Of those 113 Black Gran Sport hardtops only 59 were made with the black painted sport mirrors. Remember these 59 cars include GS 350, GS 455, and GS Stage 1.
The car in the magazine and the car in the internet ad are both optioned EXACTLY the same. With only 728 Stage 1 built in '72, plus the rarity of black (113), and the black mirrors (less than 59 Stage 1s with these), the chances of two cars both with black vinyl top, N25 bumper, 15" wheels, black bench seat interior, sport steering wheel, AM/FM radio (with an 8 track underdash), PS, rally gauges w/ tach, door edge guards, and very low miles, is too much to ignore!
Also, if you look closely at the engine shots, here is the thing that confirms it for me: in the magazine you can see a paint inspection mark at the 12 o'clock position on the top of the brake booster (can't see it however in my scans, but it is visible if you have the magazine in your hand). The same paint mark is visible in the internet ad.
Also, the "Stage 1" sticker placement is the same on both cars. Why is this a give away? Because the decal is normally about 1" closer to the wingnut so that the radius of the decal matches the radius of the air cleaner lid. Well both the car in the magazine and the internet car have it place all the way to the bottom. The is probably original, but just a very unusual placement. Too much of a coincidence for 2 identical optioned, very rare, low mileage cars to have this the same way.
Also since the car was in the magazine in 1987, it appears that someone has replaced the original upper radiator hose (which had a white stripe on it). Also the master cylinder has been replaced. You can tell 2 ways: 1) the plating on the lid is much newer looking than the booster 2) the original master cylinder on a disc brake '72 GS has bleeder screws (as shown in the 1987 MCR article).
Bottom line, got to be the same car. Not sure why the sellers would be so adamant about it not being the same car, but it has the same car.
Also a guy on the Buick bulletin board owned the car until recently. go here :
http://www.v8buick.com/showthread.php?t=183530 and scroll down to post #5.
