I found used 19.5 visions and 265x70 tires that were about 85%. I only had to pay $1400 which was a steal here in Alaska. That was 4 years ago, and I am still running them. They help tremendously with sway, but if you drive empty... They are rough. I have studded 16's that I run in the winter. And I have another set of tires if I am not going to use the camper for awhile, but we tend to be spur of the moment campers. So I havnt used those much, and so I usually leave the 19.5 s on.
Good luck! I love knowing that I can travel all over Alaska, and not worry about having marginal tires. I have traveled hundreds of miles on Alaska gravel roads and no issues loaded at 10,600 to 11,000 lbs.
Garry in Kodiak, Ak