I've a 72 Duster myself, a 408 stroker, lots of play-parts on there, dyno'd 543 hp / 572 tq. TTI headers, 2.5" exhaust with an X pipe...etc...etc. I've been running Flowmaster 40s dumped at the axle for about 2 years. They're louder than hell dumped like that, stunk the car full of exhaust if...