Ya, check blow by, Check for moisture/antifreeze on dipstick, Make sure the guy doesn't start it for a day or so before you look at it. With decent batteries it should start at 5-10 below C with out either or plugged in.
Also outright ask the guy how it runs, if he has done the pump/injectors and or turbo? The combination of hours and age I would do all three as well as the lift pump down at fuel tank if he hasn't .
Check the condition and how clean the rad is . Check coolant level and look for oil scum on rad cap.
If you have time pull an oil sample after it has ran for a while and send it away.
We have a 466 in the one 1480 we still have (don't use anymore) and 2 in 4366/86 tractors. Except for oil leaks on the 4386 they have been great engines, excellent cold starters.