Pontiac’s second-generation Trans Am was supposed to launch with the rest of the 1970 lineup, but tooling delays pushed it to a February 26 debut — creating a “1969 1/2” nickname collectors still use today. From the Ram Air III and IV through the emissions-fighting SD-455 and the shrinking engine lineup of the mid-1970s, the Trans Am’s first six years tell the story of muscle car performance colliding head-on with new safety and emissions law. Read on to see how the numbers changed year by year.