Not to sure on that but i run stock 245's on aftermarket 16x8 wheels with a 4" back spacing and they damn near hit the front inner fenderwell, and if i lower my t bars 4 turns for racing they do hit!!!
I just put a set of 265/75/16's on mine and they are just about right. If I recall correctly a 17" Dodge wheel will match up perfectly, but they are expensive. Weld makes a few different styles in 17's but get ready to shell out the $$$$. Looks tough though.
Depends on backspacing...but I bet not much wider than 8"...my 8" wide rims with 4.5" BS and the rims are about even with the fenderflares. My tires stick out a little bit past the fenderflares. Check my photos.