On my 72 Cuda, I have a 3 inch TTI system, but I got the turn down pipes at the end. Keeps noise down, and keeps exhaust out of the car. I also took off the rear valance, and got a fuel cell. I like the look from the rear. All you see is the 8 and 3/4 differential and tires. I used black spray paint in the differential area as well. Taking the valance off allows air to escape from under the car well, so you can be faster. Just foolin around. I'll put the valance back one of these days. I also have some stainless straight exhaust tips I might put on. They are 5 inch in diameter. Look cool!