help me choose tire for 15x10 wheels

[Project86]

I have a set of prostars to put on the back end of my truck. Only issue Im having is figuring out what size to order.

I was looking at some 255/70/15a. Which are roughly 29" tall. However it says a max rim size of I thing 8.5"

I have 275/60/15 on the back now. But I don't know if it will be the look I'm going for

I'd like to have a wide tread width. Tall sidewall and roughly 29-30" tall tire!! Please help! I'm plan on doing my shopping online.
I found some hoosier quick time drag radicals which look nice but I don't want to spend so much on tires