single exhaust for 318...what size??

are you building the system or taking it to a muffler shop? for what it is, you arent going to be setting records, go with 2 1/2 or 3" off the headers, you can do the 2 1/2-3" flowmaster Y not sure if they offer a 3-3, maybe magnaflow does. run 3" right out the back. no need for 3 1/2" on that car. id run the longest dynomax super turbo, a hemi model if you can get creative and fit it. or go with a std 14" long and run a short glasspack for a resonator next to the gas tank to keep it quiet. if you want to.