What can need replacement is the alternator, water pump, fuel pump,
hoses, belts, the heater core maybe on its last legs, the same with the
radiator. If there is a distributor, the bushings could be going.
But, these are all replaceable. My brother has a heavy duty Chevy (350
4 bolt main with 4 speed) in Texas and has 270,000 on it. All of the
above have been replaced over the years plus a cam shaft.