Both of these articles tout the car as 'matching numbers' and have other failings in their reports.
First: A previous owner of the car states the original engine was long gone when he owned it in 1998 and disposed of the original transmission after 3 unsuccessful attempts at rebuilding it. So, the 'matching numbers' statement may mean different things to different people and it's highly unlikely the original matching number drive line (with original stamping of partial VIN) is in the car.
His quote: It states in the PDF from Barrett-Jackson that the car was numbers matching but I can assure you that the original motor disappeared many years before I got the car. It could have had the original transmission in it when I purchased it but I was a bit naive about the numbers matching thing and disposed of the transmission after 3 unsuccessful tries having it rebuilt.
Second: The first article states, "...1 of 3 known real Black cars..." I cannot attest to how old the article is but the LS6 Registry has several black Chevelles listed; not all convertibles but the article doesn't state body styles and is misleading and/or uninformed with "...1 of 3..." statement.
Third: The BJ article claims a 4.11 Positraction rear end which was never offered in a Chevelle.
Barrett-Jackson auction, 2005.