single exhaust for 318...what size??

You must want the stealth/sleeper look. Whats the HP level est.?

IMO, unless your looking for the sleeper look, you would be alot better off with a simple system ethier like a Jegs/Summit racing dual exhaust kit or a Pypes exhaust. A fella here just posted a Pypes set up on his Demon. Looks good.

http://www.forabodiesonly.com/mopar/showthread.php?t=52929