May I ask why you want to use HOn3?
Most QR models are either HO or HOn3.5. HOn3.5 is known as HOm in europe. The gauge is 12mm. I'm sure there would be Tillig track dealers in the states.
Steam Era models makes good quality wheel sets for 12mm gauge track.
http://home.waterfront.net.au/~sem/
Hmm, he does HOn3 wheels too.
He mentions delrin bearings, but I use English 'top hat' brass bearings with his wheels on my NSWR stuff. That is a super smooth combination, particularly after adding a bit of pencil lead as lubricant.
Terry Flyn has some ideas about weight for Australian steam era stuff. Many wagons are much smaller and shorter than their American equivilents and so the NMRA wieght formula seems to result in wagons which are too heavy. Here's a link to his site:
http://www.angelfire.com/clone/rail/index.html
I think you'd have to go with 12mm gauge track. However, my Indonesian railfan friends use trains running on standard 16.5mm track, even though their prototype is 3'6". The Japanese also run their HO models on 16.5mm track although their prototype also uses the 3'6" gauge. Some QR modellers also used HO standard gauge many years ago, but the 12mm gauge seems most popular now, even displacing the old Sn3.5 favour (S scale on HO standard gauge track).
And don't forget about the buffers. Buffers mean more cleanence is needed on curves. So even small, short cars need #6 turnouts and 24" radius or larger curves.
Let me know if there is anything you need. I am well placed, and I have the right knowledge to help with your project.
Regards, Paul