Everything except the engine. These are junky trucks. VP44 injector pumps fail often, and plan to replace the factory lift pump first thing if not already done, which is huge contributor to injector pump fails. FASS or AIRDOG type after market pump, never the in-tank one.
Ball joints may or may not last.
front end junky.
front hub bearings hard to replace.
drivers seat cushion will wear and slant to the left.
the 4500 trans is particular to fluid and can be destroyed with the wrong stuff (yellow metals and carbon fibers), and the main shaft can fail. The 5th gear is an add-on gear and has issues, can be corrected.
There is a Death Pin, needs to be fixed if not already. priority.
On high mileage ones look for Tappet gasket failure (lots of oil on left of engine block).
on 4x4 the oil pan is very difficult to remove, requires front end compnoents to be removed.