In most high milage things, it's better to replace typical "wear out" things before they puke on you on the side of the road.
For me, every 100K means new belts, fluid flush, new cap, rotor, plugs, wires, points (if applicable) fuel pump, and a close examination of both the starter and generator/alternator.
Tires, fuel tank inspection and flush, radiator flush, new grease in the differential and tranny, brake line, fluid, pads, drum inspection.
A valve check and adjustment dosen't hurt, either.
I guess that isn't really an overhaul.. more of a tuneup than anything.. but again, i'd rather not discover problems on the road at 1AM on the way home from the auction.
Guess the old saying "an ounce of prevention is worth a pound of cure" rings true to anybody who left the proverbial sleeping dogs lie only to discover their in tank fuel pump likes to puke when it's least approperiate.
