Earliest known..??.

[1967Z28]

Chevrolet did give out parts to some racers. Maybe not as directly as Ford and Mopar but it did happen. Fred Gibb did get a cross ram for Little Hoss and this was before he became more high profile with the 396 Chevy IIs and ZL-1s. Ken Deckman, a Pacific NW Trans-Am racer had a cross ram show up on his door step even though he already had one and didn't request it. I believe he got an extra GM fiberglass cross ram hood under similar circumstances. If a local race was coming up you might get a little surprise in the mail. Chevy also had stuff like experimental rear axle assemblies that they would send out for people like Penske to use. Normally they would want something like that returned so they could tear it apart after the race to look at wear characteristics or, in the case of failure, to see why it failed. One of these axles from the Penske Camaro that won Sebring in 1968 stayed with the car and was never returned. It may have had to do with the fact that Penske sold the car shortly after that race and the car went to Canada. Stamped numbers found on the axle housing decades later were confirmed against internal GM records to correlate to a Chevy Engineering test assembly. Bottomline, I'm sure guys like Jenkins got stuff given to them under the guise of testing product in heavy-duty, real-life situations but it wasn't anywhere near what the other car companies did.