The ZR2 special engine package was a $1,747.00 (1 year only) option originally planned for 1970, but officially released in 1971. It included the special equipment in the ZR1 package, but for the 454 LS-6 engine. Per GM policy, 1971 Corvette engines were detuned to run on low-lead fuel, "except" for the LS-6 V8, which was rated at on premium fuel. 188 cars in the 1971 model included the LS-6 engine, with only 12 with the ZR-2 package, including only 2 convertibles. Some believe the "ZR" lettering to stand for "Zora Racer", named after chief Corvette engineer Zora Duntov, but in 2008, Corvette Production Manager Harlan Charles said, "the reality is the codes are usually random and get meaning from enthusiasts."