The sites out there are designed for the later style 17-character VIN.
You could start by requesting a DMV registration search in the state the car was sold in. The state may not comply or redact names from the docs. If the car has not been registered for some time, it drops off current records. Generally speaking, DMV records are only maintained for 10 years. Another issue, not unusual for people who buy collector cars to not title or register them. The current owner of record may have sold it years ago.
Back in the day, salvage businesses were not required to report scrapped VINs as they are now.
If you have a contact with NCIC access they could run it for you. Law enforcement can and did do that way back when, those days are long over.
I have been watching online and auctions for over 10 years; the CRG has a db of 1st Gen Camaro VIN info. That VIN is not in any of the records I have.