Thanks all, this isn't my first rodeo so I'm aware of the pitfalls of lack of sound deadening and rattling trim. The plan isn't to turn it into an SPL weapon but to increase the sound quality significantly, a little deadening/damping material can go a long way without introducing a lot of weight. I'm mostly interested in custom fabrication in the wheel well at this stage, looks like fiber-glassing might have to be the way to go, this looks ideal:
http://www.ft86club.com/forums/showthread.php?t=38852