Hmm,
Good question... my limited knowledge of the sixers are going to show here.
But considering you might want to save some torque on the low end (especially running a six), I would opt for a single exhaust with a dual conversion at the back.
As my experience with base models are limited, results may vary...
__________________
Uncle Sam
"What the hell is up with all the gauges?
Calling Captain Kirk, your ride awaits... Phasers on stun...."