Hi there, I am looking at purchasing this 66. The muffler (pictured along the front side of the gas tank) is surprisingly quiet and definitely all wrong on any Mustang. I had original flowmaster 40s on my Foxbody which were great and no 'drone' issue at higher speed as the auto gearbox had overdrive to quieten things down just enough. So my question is what's the simplest muffler swap to do to get the right balance of sound at idle, when accelerating and when cruising - gearbox is a three speed auto. Thanks