ljensen,
Please do yourself a favor and go to this website
www.tirepros.com . Click on the dealer locator tab and type in your zip code to find a
proffessional dealer near you.
The information you were given isn't exactly accurate. Being in the tire business, I see all types of wheels, axles, and tires on a daily basis. There are
many 8 lug heavy duty aluminum wheels on these and other trailers
not rated for 110 psi.
I'm not 100% positive, but I believe the 7000 pound Dexter axle has heavier bearings, spindles, and heavier duty brakes than the 6000 pound axle. A call to Dexter would probably be in order, and I will do that today.
Clearance is not a problem. I haven't seen a fifth wheel camper yet with ST235/80R16 tires, that the LT235/85R16RST G614 wouldn't fit, with room to spare.
I will post my findings on the axle when I get an answer.
On Edit - I have spoken to my axle dealer and discovered the spindles and bearings are the same on both the 6000 and 7000 pound Dexter axles. The difference is in the wall thickness of the axle tube, with the 7000 pound tube being thicker.