The Gear Vendors gear splitting helps a little on hill climbing with heavy trailers. While you technically will have 8 gears, some of them will be so close to each other that they are useless. You will have a double overdrive (the 4L80E is already an overdrive transmission) with the Gear Vendors. If you like to go 75/85 mph on the open road then the lower rpm's with the double overdrive will be nice, but you will only get this speed with a bare truck, not towing any significant weight. You might be better off spending your dollars on power enhansements for the truck rather than the Gear Vendors.
83 C10 Suburban, Silverado, 6.2, 700R4, 3.73, 31-10.50R15
82 C30 Crew Cab dually, 6.2, Banks, Th400, 4.10, Gear Vendors, 235-85R16
83 C20 Suburban, Sierra Classic, 6.2, 700R4, 4.10, custom paint, 285-50R20
95 Yukon, 6.5, 4L80E, 3.42, 265-50R20
73 GMC Astro 95, 8V71, 10 speed Roadranger, 110" WB, 6 each 11R24.5