Thanks for this. I own a 66 coup with Dynomax 17731 mufflers which are still very new looking. The car needs an H pipe. The rear pipes are about 1.75 inch which are new. Was thinking of putting a brand new system in but now thinking of just installing an H pipe as one of the single pipes has a leak at the manifold ( does not line up properly). Also the rear hangers are attached to the floor not the frame rails or does that matter? I don't mind the sound just would be quieter without the leak.