Can anyone tell me what the difference between a 72 model and a 73 model is, most sites don't even cover 73 models. I have TTI headers on a 340, and putting x pipe on then not sure what mufflers yet..so I looking for recommendations there too!, and then I have put a fuel cell in the trunk to allow for 3" pipes to the rear bumper because they would have never fit with the stock tank in place, the reason I'm running 3" is I stroked it to 416 and am going to be quite a bit north of 625 HP. I should also mention I put a Ford 9" trussed rear end differential, that's why I lost a lot of room, so I fuel celled it. They make mandrel 3" tailpipes for a 72, but not 73.