But in my opinion you shouldn't even be thinking about mpg when looking into gears to match 35s. You should be thinking about what gears would best put the engine into that sweet spot of torque in the power band. Doing that would produce the best drive-ability (and as a bonus that should also give you the the best mpg). I would go with 4.88s personally, but 4.56 should be fine too.
But regardless, if you've got 35s right now with stock gears, any of the 4.xx ratios will produce better mpg so you should see some improvement either way.