If you can afford it there is really no substitute for ARB's front and rear. It is the strongest, most reliable, and flexible setup available for your axles. As long as the air lines are ran correctly and the internal air seal is installed correctly you will not have a problem. The ARB carrier is STOUT. Far stronger than the factory carrier (that you have to reuse with lunchbox lockers). You do not want the carrier or gears to be your weak link. Far cheaper and easer to swap an axle than a munched carrier / gears. Plus you get the street manners that you can only get with an unlocked axle not to mention the better trail manners and less wear and tear on your drivetrain. If you do have an issue with an air line - the plastic air lines are easily trail repairable - and if not - you still have a working vehicle. The locker just won't be locked up. Also, if you order before April 30th and get two lockers - ARB will give you their high capacity compressor and air up kit for free. Buy them on ebay, use 8% bing cashback, and you have a hell of a deal.
I read the thread and wasn't sure if you are doing the gear/ locker install yourself. If you are, and haven't done one before, you should have someone help you with the setup. It's not technically difficult, but having experience along with the many tools that are required to do it correctly is necessary.
As far as 4.56 and 4.88 - there isn't that big of a difference ratio wise between the two. Not like the difference between your stock 3.55 and 4.56. There is however a strength (some may say overblown) issue of the 4.88 ratio when installed in the D30 front. You end up with a pretty tiny (and weaker) pinion gear and is also a little bit harder to setup and get a good pattern from.
