How many ZL1s did GM give to racers?

[GRB]

I have been under the assumption for years that GM gave one to Dick Harrell and one to Lamar Walden. At the last SEMA show I attended, probably 8 years or so ago I bought a Camaro book from the author of the book who then autographed it. We were just standing there talking and somehow in the conversation he said that there is no record of GM giving a ZL1 to anyone other than Dick Harrell. I didn't know what to make of this and didn't really care. Now I have heard that same thing again.

Maybe it's one of those memories that have been obscured by time or maybe there is some real proof somewhere. I tend to believe what I've always heard and that is that two racers were given cars. Is there another opinion and any proof of it?