The main one I can think of are jubilee clips on the oil cooler hoses if they have been extended. I saw one that looked OK but the pipes were clamped with jubilee clips and when the engine was serviced the increase in oil pressure from fresh oil caused them to blow and he lost all oil and ruined the engine. The other thing I have seen was no oil cooler as they used the old radiator and the pipes that should go to the oil cooler were just connected to each other creating a loop. Also a lack of intercooler too would wind me up a little. Although it doesn't need it if the conversion was done correctly it should have one.
If it's had an electric fan fitted, just make sure it works. And look at any changes to the loom. Personally I hate crimped wires with those blue ends and I certainly dislike clip on joiners. I can't see an issue with soldering wires, but each to their own I suppose.
The temperature gauge might read too high too if they are the original dials and the Discovery temp sender. Just make sure the engine isn't actually running too hot.
Make sure the oil pressure warning light comes on and goes out when the engine has been started.