I replaced my 73 flat tops mid December. I live close to their shop,Steve was REALLY helpful setting it up. I also pulled all smog at the same time It's a different car. It's the most fun in second punch it at 2500RPM the rear squats and it's stump puller to 5500 and keeps pulling to redline. The only problem was my gas mileage dropped for a couple of months as I developed a lead foot. Best money I spent on my Z.