Greg,
Good luck with your 'velle projects. Way to jump in w/ both feet. My '69 L78 coupe is an M21, KK rearend, Olympic Gold, black bucket interior w/ 71k documented original miles and was delivered to Colussey Chev. in Bridgeville, PA (suburb of Pgh). My Mom and sister live within 5 minutes of the dealership. The engine, tranny, and rearend are original to the car. Colussy is still in business today (although they moved down the street a bit). You may want to check with them (probably a needle in the haystack, but this was not too far from Forbes Field where the Bucs played at that time). I plan to contact them to fill in a few more gaps with my car. The 1st owner was a returning Vietnam Vet pilot whose family owned a Quaker State Service station. He took good care of his car (each oil change, service, and repair was recorded in the owner's manual). I am still tracking him down, but have spoken to two of the former owners to date. I am fortunate to have 2 partial buildsheets, the owner's manual with all services/repairs recorded and the POP for this car.
Will try a link to my 69 velle L78:
http://community.webshots.com/album/164998594CGZLzd
Good luck,
Sam