I just found your forum, and had to join. Finding fellow-Gibson bass players, alone, is certainly worth it.
I began playing bass back in the mid-80s, when I purchased a '76 ebony Thunderbird (for $400!) and fell in love with it. But, sadly, not enough to keep it, and it went the way of selling and buying, and buying and selling, basses, which continued for the following decades.
Then, about 4 or 5 years ago, I happened upon an ebony '79 Thunderbird. It was in fantastic shape (no headstock crack) and was reminded why I loved these basses so much. So, I bought it. During this time, I began reading the (possibly apocryphal?) claim that Gibson shipped only 7 ebony Thunderbirds in 1979...at least according to the Fly Guitars website
http://www.flyguitars.com/gibson/bass/Thunderbird_1976.php which quoted Larry Meiners' book "Gibson Shipment Totals 1937-1979". Almost exactly a year later, I saw that another was up for bidding on eBay. So, I bought it.
Flash forward to today, and I'm now looking at this ridiculous collection. All ebony. All from 1979. All sound amazing.
(By the way, The Guitar Dater Project webpage was very helpful in determining on what days the basses were produced at the Kalamazoo plant)
cheers!
Andy