I'm interested to see what you learn, because I'm planning on doing the exact same thing. I spoke to my local tire shop (not a chain) and they said they were happy to install 255/85/17's on the stock wheels, and they emphasized that I should not do anything that required spacers.
I'm planning on doing it after I get some mileage out of my Nexens.
As I live where winter can turn ugly, and (1) there is an outside chance I have the truck before winter is officially over here, I am leaning toward just replacing the Nexens immediately so (2) as to keep them close to new when trying to resale them to an interested hotshotter, or otherwise. If anyone is interested in them, I'll have them available sometime around January to March it looks like; located near Fort Collins, CO.
BTW for tire shoppers.... I've had Falken Wildpeaks AT3W tires on two rigs, and Mickey Thompson Baja Boss M/T 33x12.5x17s on my Jeep. I would not hesitate to put either one on any type of rig. Ever!
I wanted the Baja Boss A/T for the Jeep but they weren't in production yet, so I went with the M/T. Great tire. I am betting the A/T 255/85R17 is the perfect tire for these trucks that are going to be used for their purpose and daily driven too.