Thanks everyone for the feedback! It's greatly appreciated! Especially TrailJeeps, great write up!

Fortunately most areas I'm driving are relatively flat, Australia isn't all that mountainous, especially around Sydney. And our highways are through flat country.

Due to wanting to keep strong enough teeth and in consulting with a few other Aussies, I've decided to stick with the 4.56 I already have the ring and pinion too!

The reason I'm using a D30 is because I got one with all the work done for $150, truss, gussets, sleeves, HD ball joints, you name it, it just needs some internals. Down the track my plan is to get either a Terra or ProRock 44/60 combo.

I might consider changing the ratios at that point with the new diffs, however seeming I've been fine on 3.73 and 35s for a while, I'm keen to give the 4.56 a good run for a while.

Again, thanks everyone, happy Jeeping!
Now just to decide on what rear locker to get... lol

 

A Dana 30 is a remarkably strong axle for what it is. While I'd always recommend someone who's planning on 37s out of the gate to either purchase a Rubicon or swap in a D44. But, if you're building up, like the OP, run that D30 until it dies! It'll last a long time if you understand what you have a drive accordingly.

A selectable locker is best, used sparingly, and the other solid option is a Detroit Truetrac, which will get you anywhere with proper throttle application. Add some gussets and you're good to go. Don't let a D30 hold you back.