They did race 1st gen Camaros at Daytona and Sebring but I have not heard of a factory big tank Camaro.
I checked the ad for the 67 Yenko Stormer Z/28 which lists about 20 options and mods but no big tank.
Fuel was a issue on the Penske cars. If you read Mark D. book he mentions a special filler neck that held a few gallons and got a lot of attention at tech inspection.
