Tim, I've got a pair of Yokohama 8.25 radials, but I don't think they make them any more. These guys have 20" tube required in Bias. Samson is one of the better Chinese brands. I use them on my forklifts.

http://www.nebraskatire.com/truck/car

Their top of the line is Yokohama. They could tell you whats available. They might still have some NOS