Nissan Patrol SWB for towing.

I've had both SWB and LWB TD42's (manual) and by far the best truck to tow with is the LWB. It bounces around far less and in my view is still one of the best towing vehcles that money can buy.

I have had SWB '88 (diesel TD42) Safari for over 12 years, needed to tow a boat just under 2.5 tonne.
A LWB may be quite a bit less expensive, as they're not in such demand by the serious offroad guys, especially the high-roof models.
Non-turbo doesn't have a lot of power, but weight balance, braking etc is perfect.With 5 spd, there's a big ratio difference between 2nd and 3rd, and with non turbo, I find that towing up hills, then 2nd gear is much too low, but it'll drop out of the power band in 3rd. An original turbo will cost more than equivalent non-turbo, and the turbo is another eventual maintenance item, so only you can decide if that's what you need.The turbo will be much nicer to drive when towing.
Heed the advice above re fitting an auto transmission oil cooler, if it hasn't already got one.If there's a weak link in these old Safari's for towing, it's the auto trans.5spd are a bit hard to find.
The odometers are often not aligned and trip meters don't reset to zero, because of crap plastic used in the mechanism. In other words don't rely on "misaligned digits" to indicate that it's been clocked.But be aware that there's a lot of incentive to disconnect/clock all diesels in NZ, because of high road user charges.Check the history thoroughly.
Be wary of one which has had mods to injectors/injector pump or an aftermarket turbo (probably including above mods).If it hasn't been done right, then seriously expensive engine problems can be the result. The motors, if looked after, have been reported to be still running well after over 1,000,000 km without having the head off.
The rear windows rust out (bad design).Can be fixed by removing the sliding window, cutting the rust out, and fitting a plain glass window.
Other rust spots are on the body either side of the radiator, near the chassis mount (a hard spot to inspect unless it's on a hoist, and you'll still need a good light), and on a body seam running across, above the rear axle.The latter is potentially terminal.
Rear brake callipers can be an issue, and missed by some WOF checks.
"Speed wobbles" at 90-100km/hour is very common.Usual cause is worn panhard rod bushes - replacing them is not a big job.But if the suspension isn't standard (ie lifted), or it's been pranged at some stage, it might not be the panhard, and a more serious matter to put right.
The injector pumps are good, but will suffer leaks at some stage. The first seals to go are often some which are accessible without even removing the pump, but be warned that if this has been done without a full recond, then other seals including and especially the seal around the pump drive shaft and the shaft itself will not have been replaced when they should have been.That can result in (dirty) sump oil getting inside the pump, or diesel leaking into the sump - both very serious issues. So if it's being sold with "recond pump", ask for the receipts.If the job cost $200 or something like that, then it wasn't a recond pump - it was a cheapo fix so they could sell their problem to you.The engines should pull quite strongly through to red-line.Many don't pull well beyond about 3,000 rpm and that's often because of stuffed injectors. (could be other things too).Fact is that except when towing, you don't really need to rev them above 3,000rpm anyway, so people just don't get injector issues sorted, even though they'll be blowing black smoke, and wasting fuel.
These potential pump/injector issues should be seen in context. The pumps and injectors will last as long or longer than pumps and injectors in modern common-rail diesels, but in old diesels like Safari or Cruiser, cost to recondition will be only a fraction of the cost for doing the same on a modern diesel.
After 12 years owning and doing pretty much all maintenance on my Safari myself, I'd still get a diesel mechanic to check one over before I bought it.