3.5" is correct, but 2.5" will push the wheels out a little from the fenders. you'll also have deeper dish wheels in terms of looks. not sure of the consequences to the wheel assembly long term though. i did it to mine, and it looks super cool, but there is a little concern in the back of my mind.
I have a set of wheels for shipping cost if anyone wonts them! about 3.5" BS. ther rub on the tie rod When I had 33X12.50 on them. The won't rub with 31X10.50 or Maybe even 33X10.50. They are chrome steel wheels. with about 8 holes in them. They are in great shape just don't have room to keep them around!