I'm planning to convert mine to 6 x 5.5. I picked up a pair of Dexter 3500lbs hubs from Straight Line suspension in Mesa. They fit fine. I highly recommend this place for any trailer parts or questions. Mike was great to work with.
I want to install the same 5 spoke Tundra wheels and tires (255 80 r17 BFG KM2) as my truck so I'm sourcing the studs now. It's been quite the task to figure this all out.
I'm picking up the studs this AM at Vatozone. I rough fit the combo last night after removing the original hub and the fit looks good, maybe a little close to the frame on the inside. I may have to have a 1/2 to 1" spacer machined (and longer studs) to get the wheel centered perfectly in the fender but I won't know until it all goes back together later today. Clearance from the top of the tire to the fender looks good. I would not expect any rubbing.
I did buy the wheel spacer/converter mentioned before but pushing the wheel out by 2" put it out to nearly rubbing on the outer fender verticle lip so I'm trying the hub conversion route now. If the hub trick does not work I'll go back to the OEM hubs and spacer and then I'll modify the fender to get the right fit.
Rudster - question for you, can you tell if your Trailblazer axle is OEM or has it been modified at all to accommodate the heavier rims/tires by the previous owner?