I would look at who is selling it, if you are buying it at a good or reduced amount because it is old then you can't expect it to not have a few troubles but if it's lasted that long then it must have been built well.
If you are paying serious money then take a machanic, hours aren't the greatest way to look if it's had use or not, what you are really looking for is oil leaks or slow to start.
Where are you going to look? how much?
Shaun