have you tried roadtrek:
http://www.roadtrek.com/brochures/
pull down menu will get you the 2013 ( or about any model year) brochure.
youtube has a couple of pretty good videos from dealers which run through the features.
I believe the 170 uses the lighter chassis which is good for MPG, with a 6 speed tranny and the 4.8L.
I have a 4.8 in my 2001 Sierra ( 4 spd auto) and at 160,000 miles is flawless. mpg at about 18 at 70~75 mph. expect less maybe with a heavier van ( but the streamlining + 6 speed will help)
I assume you have been in a 170- kinda tight and they sleep sideways, so how tall are you?
Mike