Hi Richard,

Well, the timing belt should be changed at least every 150,000km or 10 years for a start. They're very robust trucks in general. We know that the brakes can squeal if the pads are fitted without anti-squeal shims and the air conditioning may be a bit rubbish until the compressor clutch relay is replaced, but that's about all there is to look out for. 

These are hard-worked vehicles, so watch out for body damage, underneath as well, and fluid leaks and the like.