It can be done but the tires may be hard to seat on the rims. Also, the end result will have ballooned sidewalls so the combo may look a little odd. I have 12" wide rims on 35" BFG's on my crew cab. They're ok for now but next time I may step up to a 14.50", wide 36" tire so it will look more "natural".
Something I noticed when doing mine, the tread shape will effect the overall look a lot. For instance, the BFG All Terrain has a very square cut shoulder on the tread making the "balloon effect" much more noticeable and looked awkward. I found that the BFG Mud Terrain K/M has some cleating that wraps over the shoulder onto the sidewall a little. The wrap around of the tread helped to make the combo more eye friendly.