SOA! ahh hahaa I am also in the planning stage of this seemingly 'simple' task
I've just been in touch with a diff reconditioner and he's suggested an alloy ford 9" centre with 4.11s and a custom housing...
they can do it two ways, weld in the std nissan tubes and use modded nissan axles, or go for a fully manufactured 9" housing with floating axles.
the reason they weld in the nissan tubes is so they can rotate the centre to reduce pinion angle on the rear uni. neat and professional. Great, except you have to do it the 'legal' way and buy the raised springs, dropshackles etc and not actually do the SOA (it's illegal in some states here) benefit is great articulation in off-road instances, but on the road it's a wallowing nightmare, thanks to the shackles. Problem? yes, it defeats the purpose of an SOA, especially in the $ department.
The Ford 9" is plentiful, cheap and simple. The hituff axles aren't. Floating hubs aren't either, but in the long term, costs aren't a problem. it will save you at least 2 standard diff rebuilds... Custom fabricated housings are easy, making the SOA cheap and very customizable. Rotate that diff and reduce the pinion angle, extra shock mounts, add a panhard rod or watts linkage or trailing arm mounts... it's all easy to do at once, even if you don't plan on it just now, a few extra welds on a housing is cheap now. Locker diffs, LSD's open wheelers... you name it the 9" has it in plentiful and therefore cheap supply. Stud pattern and offset, axle length, disc or drum... it's all possible to do quite cheaply, using parts from other vehicles you can source at a wrecker. Disc brakes are a good cheap mod, and I did one for an MQ using late model Chev bits, but the owner wanted a chevy stud pattern,for his new mag wheels, so it was a simple conversion. Chevy suburban's are ideal donors. 4 calipers, stubaxles and rotors 100 bux all up. Once we had a stubaxle, it was wasy to find a match for the floating hub to get the correct stubaxle and wheel bolt pattern. Then the diff dude went to town, 31 spline axles, LSD centres with 4.11s and discs all around. 2 complete axles (front and rear) for 2800 aussie dollars. and it makes a huge difference to the handling!
and believe it or not, the cost isn't that much different between either method... Bloody Expensive!
I've been in one thats had the conversion and a 4" lift. and it really handles well too (yes I thought I was going to fall out when we took a right angle corner at 45 miles an hour, but we went round with a bit of body roll and tyre-squealing) Either way its a pretty serious foundation for all your patrol's surefootedness. Do it right and it's going to make a huge difference in the overall ride and articulation!
I didn't quite have a heart attack when i hit a ballpark figure for a G60..., but I was planning to run 35x16 Baja Claws which necessitate the conversion... So much so, that because it's too cost prohibitive (compared with original plan), I've decided to go all out and go for 37" tyres, the cost difference is naf all, so get the diff centre rotated, the new perches and look for an alloy 9" centre (weight savings!) with the hi-tuff axles and floating hubs, spend the few extra on a rear disc brake conversion,
Like i said, not much dearer than finding a replacement stock diff, reconditioning it and doing the SOA on the stock housing.
so glad I've got spares... I'll be able to keep the stock diffs spared up for about another 25 years... just in case I change my mind :o)
Joe.