Exhaust opinion

With a teen there will be no loss or gain either way I would think. I do know that my 88 D350 came factory with 2''dual exhaust,no cats(over 8500 GVW) that feed into a single 3'' tail pipe after dual mufflers. It was a 360 4 bbl factory. Now it has a 318 4bbl. I was thinking on the same lines as you that when it needs the exhaust replaced I will go single 3'' for ease and weight reduction. Lots of pipe under there that run side by side on the passenger side of the frame. Just a thought.