If you need to drive in snow and ice and still want a locker, you definitely should get a selectable locker instead of an automatic locker. This is because you need open diffs to drive on ice and most snow. But it's very handy to also have the locker available for deep snow. If you have a foot or more of snow, lockers are fantastic and make a world of difference. I drove all over the place with 30" of snow when I used front/rear lockers in December while other 4 wheel drives were getting stuck by following my tracks.

For ring and pinions, two of the companies generally accepted to be good are Yukon and www.precisiongear.com