I posted this eleswhere but it might be of interest (things we learned when shopping around):
Only recently bought mine, but we looked at a few...
A couple of bits I did notice (apart from the usual checks):
Our injector loom has been replaced. It has a black conector at the end of the rocker cover, they were red originally from what I can gather. Can't be certain but it would seem that black is the modified one. Only £40 anyway.
Door locks - every one that we looked at had a lock that didn't work from the remote. Mine was the drivers door so it was obvious, but others were rear doors so you might not notice. A new one is £45 from Gordon Lamb on Ebay (by far the cheapest). You can't replace just the solenoid, you have to buy the complete mechanism.
If they have been regularly and correctly serviced then there shouldn't be any problems with the dowels. If they have had a new head on then I'd be walking away, it means it's probably been neglected. We were offered one with £2000 worth of work done (head replaced, steel dowels etc) at 80k miles. I didn't feel reassured.
A few of the manuals we drove had a slight judder when letting the clutch out. We started to think it was normal, but obviously it isn't. Ours doesn't do this.
There will be a noise when you switch off the engine. It's the oil filter winding down, nothing to worry about when you know what it is
Not sure if you are bothered about a difflock, some have them, some don't. I think that the earlier models did, then the mid models didn't, then the later models had it in the box but no linkage to the selector If it's important to you then I'd research this some more, or buy one that you know has it (ie the selector moves over!)
I opted for the manual, my personal preference. I know that the autos seem to be prone to the gearboxes running hot and cooking oil, another reason to get one with full service history (then change the oil every 12k instead of the scheduled 24k).
Hope some of this is of use. We did A LOT of miles, looked at A LOT of trucks before finally finding what we think is a good 'un.
Cheers, M&S