With a 20x10, your backspacing is probably going to be 4.5". The tires will stick out a few inches, but you'll probably be fine. You may need to trim a tiny bit off of the plastic valence on the front bumper, but that's probably it. It'll look tits though.
As for gears, 4.10s would be ok for towing, but 4.56 would be ideal :imo. It would give you a fair bit of grunt back.