1- it is highly recommended that you go with a PR
, Currie, TF, or G2 D44 instead of a Rubi. And when installing a new aftermarket 44 or would be better to spend your money on aftermarket ball joints opposed to stock ones.others can better tell you which ones will give you the best baby fit your buck, but you don't need the Pro steer.
2- yes the ARB cover is thicker and stronger. It will offer much better protection for your expensive Locker and gears. HD diff covers are cheap insurance. Plus they add a little rigidity to your center section. And that reduces hear deflection which is a big factor when gears fail.
3- with the 3.6L and the manual you will be fine with 4.88, you have a lower first gear than the autos plus the more powerful engine... 37s with 4.88 will wheel very well plus be great for DD and highway.
4- I will break down the difference in simple terms; OX, made in USA (Tampa, FL), comes with HD diff cover, you have the choice of air, electric, or cable shifted, and there is a piece available that if you air system fails you can put into the locker where the shifter goes into the cover to manually engage the locker.
ARB- made in Australia, does Not come with diff cover, only air actuated, requires extra labor cost to install due to drilling of the axle center section and air lines inside the axle, it also had seals inside the diff/locker that can (and in the long term leak) they require Locker removal to repair/replace. Parts are widely available for ARB.
The price difference is OX $1000 and ARB $1200. ARB install will be about $100 more. ARB diff cover is another $200... So initial cost is $500 more. Both are very strong and with all my research no one has definitive proof of one being stronger than the other. And any air leaks that development will be cheaper and easier to fix with an OX. So that's is why I have gone with air actuated OX 35 spline.
5- an aftermarket front 44 is much stronger than a Rubi so you don't need to truss it. As for the rear, the stock tubes are a little weak. I'm going to be installing the Artec rear truss. But remember your rear takes more abuse than the front so 35 spline is more important in the rear than the front.