I just put on a offroad x pipe with stock axle back. The axle back has been modified a little with muffler bypass holes. Actually a little quieter down low compared to h. At wot it screams. I really see no reason to ever change the headers on these cars. Guys are running 9's with stock headers and resonators.
Hardware for bolting on midpipe is (4) 1.5 inch 10mm bolts, washers, lock washers, nuts. To answer your ? OP.
2014 "Cobra Jet" GT/CS
Automatic, Comfort pkg, Oxford White