I think the Aviator used a 4-valve variant of the 4.6L V8. I don't know that engine, but would think that (i) water pump; (ii) (possibly) thermostat housing (if its plastic); (iii) spark plugs (don't laugh--especially if its got the same crap spark plugs as the 2 valve 3rd Gen Explorer V8!); and (iv) mayby exhuaust manifold gaskets. 220,000 kms is only 137k miles, so she's practically a baby! (Okay, maybe mid-life.) If your the Aviator has similar front wheel bearings to the Explorers, they are failure prone (mine went out within a few hundred miles of one another at 195 k miles). If you're planning to keep 'er a long time and to do long trips, I could see the logic of preemptively replacing those, too. (Rockauto had good prices on WJB HD's for $50/each, which have worked fine so far. Others here insist on using only the name brand ones, mostly Timken or SKF.) Once they start grinding, they can fail quickly--which could be a real problem on a long trip.
When I swapped a 4.0L V6 SOHC for my '02 Explorer (timing chains and cassettes), I decided to replace the harmonic balancer, having seen plenty of posts of them failing (separating). That balancer is a b*** to get off with the engine in the truck, and I did not want to mess with that possibility. Maybe overkill, but hey, I had 179k on the old one; it depends on how much you value confidence in your ride.
