Hi Rich,
Got your PM - and you're in luck!
Your uncle Mike's old 66 is serial SFM6S669. In the Registry it show it as sold by Hertz to Robert Lee Motors in Cleveland on 5/31/67, and your uncle as the first owner (Kent, Ohio at the time?). Next owner Asa Sharp of Akron in '68. Then Roger Hodyka of Livonia Michigan in '70 who installed a roll cage, 4wdb, 4 speed manual trans, 3.5" exhaust, R-Model apron, Detroit Locker, and TWIN Paxton superchargers

Sold to Scott Woods of Michigan in '75, Alan Stokfisz of Michigan in '82, then Steve and Cathy White of West Bloomfield Michigan in '84 who put it in the name of their 5 year old daughter Shelby Ann White in 1987. Let's see, that makes her...about 26 years old right now? Hopefully she still owns it and you can track her down. Otherwise, email Howard Pardee of SAAC through their website
www.saac.com, maybe he has some more current info on #669.
Hope this helps - good luck!
Regards,
Colin