I've found a Jeep Wreckers here in OZ and am going to do a complete front diff swap with them, bolt in bolt out. Then just buy a ring and pinion set for the rear.

Does it matter if I have an ARB locker in the back ? Surely that new ARB carriers suits the 4.10 gears ?

Yeah, or better yet you could put 4.10 in your 6spd and go to 265's Although, I think the carrier break in the Dana 30 is 3.54 / 3.73, so you'd need a new carrier in the front. The rear is ok because it's carrier break is at 2.45 / 2.56.