when I purchased my '69 in April 1976, I immediately went to the Chevrolet dealer and ordered all the trim/etc parts I thought I might replace when I 'restored' the car; at the time I thought I might do a restore in 2,3, or 4 years, but instead the car was garaged for 38 yrs instead... and my plan changed to 'preservation' rather than restoration over that time fram
I knew to purchase parts from Chevrolet even though the car was only 7 yrs old at the time because I'd gone thru the same process with my '55 Nomad (of looking for parts in junkyards, etc) before learning that even 20 yrs later Chevy still had some parts for them... so I thought to buy what I could as early as possible. I think lots of people learned that lesson also, as most parts for special interest cars *like Camaros* disappeared quickly from Chevy's shelves by people buying them up for later resale... thus the high prices for NOS parts nowadays!