Good luck on getting part numbers. I emailed Walker technical support for a list of Quiet Flow mufflers -oval, offset 2.5" inlet, centered 2.5" outlet, aluminized steel. Guy keeps telling me if I will give him the length, he will try to match a part number. WTH? - how many damned 2 1/2" oval mufflers can they make? Must be at least three, maybe four.