In 1969, due to the popularity of the Yenko Camaro, and demand from drag racers, Chevrolet opened up a path for the First Generation Camaro to be fitted with engines larger than 400 cubic inches. Previously, General Motors had forbidden mid-size and smaller models from being fitted with engines larger than 400 cu. in. Using an ordering system usually reserved for fleet and commercial buyers, two Central Office Production Orders (COPO) were made available in 1969. The first option, known as COPO 9561, featured the 'L72' 427 V8 that was underrated at 425hp. The COPO 9561 is the most common COPO Camaro, with around 1,000 cars fitted with this engine option. The other COPO, number 9560, featured the 'ZL-1' 427 V8, and can be found in the Camaro ZL-1 market.