One of the things to look out for with re-building a steering box is who does it and how.

As a very very general comment, you can get the worm gear hard chrome plated (which is something considerably different to the chrome on the bumpers and other parts!) But the 'issue' is that the worm wears mostly in the centre area, and next to zero wear at each end.So if they plate it too thick, it starts to bind at each end with new balls in there. To do it perfectly, you'd want to chrome it, then machine it so it is even.I don't know of anyone setup with the right fixtures on a milling machine (I would presume youd do it on one with an indexer and some other bits) - but it certainly _is_ doable.

Bur given the complexity involved, for my own pursuits (and fwiw my current one isn't too bad) is looking into ourcing a new rhd steering box from Nissan. Since they built utes (bakkies) in Sth Africa until only a few years ago, there's a good chance there's still some steering boxes in stock somewhere. I'm looking into it at the moment.

It won't 'quicken' the steering much, but you can sometimes find a happy medium by going to a slightly smaller steering wheel. Depending on your own physical size, a smaller diameter wheel can help turn somewhat close to 180 degrees in either direction without having to move your grip at all. With a bigger wheel, you end up hitting your legs (or at least potentially so) obviously a smaller wheel makes for higher steering effort, but on dirt and loose ground, you'd not have too much trouble with it.

I totally agree with everyone saying to avoid a completely locked diff. If you have absolutely no other option, you 'might' try it somewhere to see what it's like, but it is vastly inferior and 'hairier' than a lsd type diff (of any type) off road. Heck, they are hard enough to drive (the fully locked diff) on dry smooth bitumen. BUt on loose ground, they really screw up corner entry off the throttle, and then want to snap too easily the other direction when you apply it. They are similarly dangerous on bitumen in the wet (and no word of a lie could easily prove fatal in such conditions)

V8 supercars are (or at least were, I haven't looked at their regs in a couple of years) mandated with a spool in the rear - i.e. fully locked diff. And you could really tell if you focused on how they performed particularly mid corner, and indeed in the wet.

I've got one of the topgear 'tor-sen' style diffs (but it is not yet in the car). I can tell you for sure that they are exceptionally well manufactured, and would probably kick butt in teh application you have planned. About the only thing they 'don't' do is provide good traction if one wheel is completely off the ground, and you are stationary. But unless you are doing 'rock-crawling' it's just never going to come up in rally driving, at least not significantly. And just to play devil s advocate, if you were stuck with a wheel up, if you pull the handbrake on about half way, it'll offer enough resistance to turning for the wheel off the ground that it'd direct power to the wheel on thr ground.