I was keeping up with this thread before, but hadn't checked in for a while until just now - only to find drama. I'm quoting swirvin here because I want to make sure his truth gets read and reread instead of the asinine fits from a few ignoramuses. Danny is absolutely right for making the...
For what it's worth, my Atwood electric jacks are 15 years old now, and they support a 3,000 lb. Skyline camper, and never had a single issue. I always max out their extension when loading just to make sure I have plenty of clearance, and I just use a single horizontal support under the camper...
As you already know by now, the answer to your original question regarding fitting your truck on the trails you mentioned, is yes. In 2011 we took my old 2006 F350 crew cab LONG bed on several passes in the San Juans without issue. To be honest I think the tightest fit was taking the Yankee Boy...
Here's one of my two campers on my old truck. This is a 1998 Skyline Weekender 910 on a 2004 Dodge 3500 HO 4x4 with 285's, but stock otherwise. Pics of the new truck (also a 2004 Dodge 3500 4x4) with the other camper (Lance 815) coming soon.
Just for point of reference, your wheels are actually 16x6.5 and all GM 8 lug trucks were 8 on 6.5in bolt pattern until 2011 when they switched to 8x180mm for some bazaar reason.
I'll echo your earlier comment about the 255's being unstable at high speeds. I ran your exact setup on an identical...