i am looking at getting the classic II's and was wondering was size and backspacing i should get. i have 31'' tires on my stock 15'' teardrops now. would i get the 15x8 MT's with what backspacing? or a different size? x10, x7 ?

31x10.5s right? a 15x8 rim will work good. I have 4" BS on my rims, but I like the tires sticking out a little... here is a chart to help you figure out BS.
http://home.comcast.net/~offroaddriver/wsb/media/237401/site1009.jpg