Injector cups and water pumps are common failures.  The water pump is a serious concern; if it breaks the shaft the drive gear can get into the timing gear train and destroy the entire engine.  I took one apart that had thrown the idler gear through the front cover, bent the camshaft, broken the head, and bent about half of the valves.  Customer ended up buying a long block, and the clerk from Abilene Machine told me they recommend changing the pump every 2000 to 3000 hours.  If it has a gudgeon with a bushing you will likely end up replacing it with the bearing version if it hasn't already been done.  If you have time, the old gudgeon frame could be machined to take the bearing if you have the capabilities to do it.  Much cheaper than replacing the gudgeon frame. That age you probably want new isolators for the cab.