I really like my 295/75-16 bfg AT's....
just a little bigger than the 285.....and definitly as tall as I'd go w/ 3.54 gears and towing (granted my junk is heavier than most, but prolly not much heavier then Mike w/ camper on)...
gearing works out very well, as its 'almost' lugging it on flat ground at 60 mph....any faster and its perfect....
advantage is, dropping to 5th at 60-ish puts me right at 2200-2300rpm, and can bomb up most any hill that can justify the speed....then drop back into 6th and lug along again in the flats...
I wouldn't go any taller for the towing Mike...
yes, they are only a range 'D' tire, but the size makes them have a pretty good load rating (3400#-ish), which I've never come very close to.....(and I'm pretty anal about tire loading/weight distribution)
the M55 are a pretty good tire, but DAMN $$$$.....
--B