I just put 35" BFG's on 15" MB Predator wheels. No problems at all and no mods needed. The only rubbing I get is on the plastic skid plate and I will just have to trim the corners.

 

American Racing AR-23's work great, close but they do clear!

 

Pro Comp Rockcrawker rims work good...on a 15"X8 you have to have at least 3.75" backspacing....mine did rub ever so slightly when on a lift spinning the tire around...but with in the first mile I didn't here it anymore since then i've rotated a couple of times and wheel it regularly...

The only advantages are
...there is more tire than rim to beat off of the rocks...but i wheel mine pretty hard so thats very important
...not to mention the price is lower with 15's

The only disadvantages...
...There are less 37" tire made for a 15" rim, which is my goal so eventually i will bump up rim size!