So my dad, brother and I just picked up a 1973 Mach1 with the 351c engine at a car auction, and are looking to beef up the sound of the exhaust a bit, with some hp gains if possible. I have no experience with classic cars, so I am coming to you for some help. I've read into it a bit, and have seen things on straight pipes, X-pipes, H-pipes, different headers and mufflers, but really have no idea where to start. We'd like something that gives us that classic muscle car sound, but want to avoid something that drones a lot when we're cruising. Any advice you can give will be greatly appreciated.