Hi Adrian,
I have run a number of shoguns from the earliest model right up to the latest GDI but all petrol powered. You are obviously looking at diesel from the engine sizes you quote.
I think even on a 93 you can still get reliability but chose carefully as that's about 15 winters worth of salty roads and most will be rusty somwhere. An imported Pajero would be a better bet in that respect and can, if freshly imported, be as new underneath.
The 2.5 has two cambelts and the 2.8 is a chaincam engine both should average about 28mpg and about 20 towing, some say the 2.5 is bit underpowered for a large van.
If you find a good one and keep it serviced they will run for ever - main trouble seems to be overheating and head gaskets blowing, usually as a result of poor servicing and owners ignoring the temperature guage. Other minor electrical glitches occur but in the main they do not have major breakdowns.
Hit POCUK on google and look at the owners club forum - all you will ever need to know is on there.
On general reliability we had a 97 3.0 V6 in the family for about 3 years, it was at 54k when purchased and covered about 40K, it never missed a beat and never needed anything except service items. The new owner is known to us and is still enjoying trouble free motoring.
As you can probably tell I'm a fan of these cars, tried other makes but came back; as a tough, tow anything anywhere vehicle they are hard to beat.