Been running 35x12.50x15's on 15x8's w/3.75" BS since Oct '03. I don't recall the front tires ever having contact with the leafs.
I did the Warn 5x4.5 Hub Conversion in May '04, which widens the front axle by ~3/4" on each side due to the new spindles & hub.
You can sort of see here that even if the front was turned sharp, my tires wouldn't be close to rubbing. Statically with the wheels pointed straight ahead, the tires are ~10" away from the leaf springs.
I just measured and it looks like I only have 8" between the sidebiter tread on the MTZs and the leaf spring. Looks like my wheels are turned but I have no front end right now so it's kind of hard to tell. I *think* i did have a little leaf spring rubbing going on with 33x12.5s but didnt do any wheeling with them so I'm not totally sure what was going on there. Here are some pics...