1988 318 engine

Maintenance items like spark plugs, plug wires, cap and rotor, as well as maybe a carb rebuild if the 88 vans still had a carburetor .... NOT saying it needs them, but they could be considered maintenance items... a mechanical fuel pump (only if you have a carb) would be something i would carry on trips!

The one thing that I would consider is to replace the timing chain and gears... If you get one for a 340 (double row timing gear) they will wear better.. A

The factory usually used a plastic cam gear, or nylon coated aluminum for quiet operation. Over time the nylon gets brittle and will suddenly flake or break off and the timing chain then has enough slack to jump a tooth and your cam timing is off by one or more teeth.. resulting in really bad running, or the engine just stops..

The cam timing set and mechanical fuel pump is really the only things I can think of that might fail suddenly due to age.. On the fuel pump, if yours is still working ok, don't change it out of concern, because some of the new ones are problematic..