Other than visual, splitting the exhaust after the muffler will have no effect on the performance. Even a full dual setup with a split manifold or headers only has a power advantage at certain RPM ranges. If you want the truck to look like it's got duals, have them split the exhaust behind the rear axle and run two outlets at about frame rail width. That will eliminate a lot of fancy bends to get both pipes to clear the axle.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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