I am not sure. I know mine rub a little in sharp corners, but I think that is because of the offset on my 10" wide rims. Since you want to go with a narrower tire, then maybe you will be O.K. Maybe someone else can help you with this question.
As for the gears I have talked to a few people and maybe some of the other guys such as "Rick" could help you more, but I think with 4.56 gears you get close to the stock setup. The 4.10 gears are more for the 35" tires.
Like I said maybe e-mail Rick, Go-fast, or one of the guys that have been doing this longer then I have. I know what works for one Explorer maybe won't work for the next one.
When we did ours, I had the lift on, then went and got the tires. After they put them on and put it back on the ground, I tried turning and it was hitting, so I had to take the front tupperware piece off in order to get home. Then my dad and I cut the fenders since the next day we were going on a trip with it.
Hope this helps.