I can name the driver and car that qualified sixteenth seventeent at the April May 11, 1975, Riverside International Raceway edition of the BFG Radial Challenge: Frank Sheffield in a 1972 Vega GT coupe. DNS after a "discussion" of his oversize tires with organizers and competitors.
The field was approximately 28 racers, maybe eighteen of them actual IMSA-rules-prepared. The remainder were showroom stock SCCA cars invited to pad the slim entry, when plenty of the usual crowd failed to make the trip from IMSA's home turf. To entice West Coast Showroom Stock sedan racers, BFG offered a set of tires for the highest-finishing SS racer. Since the Vega was running on Pirellis one size larger than stock, and was a second or so faster than the next-fastest SS car, the Vega driver was offered the opportunity to withdraw his entry and receive a refund of the fee. Done.
The Entry List was published in CP&AW - whatever it was in those days - with no explanation of the DNS. Arlene Hiss whined about being passed by a too-fast Vega, in Road & Track a couple of months later. I don't have either of those documents, and would be eager to have a copy.

I have written this before, possibly even here on TNF: my racing career highlight was on that day in (new) Turn Nine at RIR. The factory Team Gremlins in their qualifying-train mode passed me at the entrance, maybe 30 or 40 MPH faster, but I made up fifty yards or more and was on their back bumpers by the exit. If I'd had some horsepower I'd have nipped them at the line. Happy moment.
Edited by Frank S, 12 November 2016 - 00:54.