I wouldn't touch any converted car myself. To many unknowns. I would do one myself but not purchase one already done. Converted cars are never the same. Will always be niggles either with electrics or mechanical parts.
I would follow John's advice and look for and probably save more than your goal for a later model td42ti. They did these from 03 onwards. So there are a few in the earlier gu3 shape before they went to the gu4 styling.
There are lots of CRD patrols out there now. I would get one 2010 onwards. Lots of mods and options for them aftermarket now too.
Car parts are getting harder to buy too. As a true parts interpreter doesn't exist any more. They just want your rego so they can just search your vin and provide parts only applicable to that vin. This will cause a problem for you for a while until you know what parts go where and can just order them from a specific part number. But no one is gonna know what drive belt arrangement you have on you ls converted patrol or even td converted patrol with current parts sourcing methods.
The only other GU would be a 4.8 and as late a model as possible. They sold these right up to 2010. However low km good examples are getting harder to come by.