why? so you can be obnoxious and have cops on you all the time? and if you want a muscle car tone, the answer is in your statement. muscle car. you're not going to be able to emulate the pure sound of a big block v8 from a little 6. It'll probably end up sounding like a boat.

 

Thats exactly what it'll sound like, a boat. I have a friend who had an exhaust on his 90 Z24...it sounded ruff

 

Lower displacement motors can sound pretty sexy. It'll never sound like a muscle car though. The boxer motor in the Subarus sound especially sexy for a 4 cyl.
http://mysite.verizon.net/res7weom/gfrank1.avi
That's a shitty 1.8L sounding pretty good to me. I happen to dispise the muscle car sound myself. It sounds beautiful at idle especially with some pretty hardcore cams, but up top its just a bunch of roaring. Ferrari 360 Stradale has to be the most beautiful sound ever to come out of a street-legal car.