I dont know where everyone is buying their shit at but I buy/sell cars aside from my regular job and have had multiple chevys with very high miles (250k+) and they all still run terrific. I used to hate them. I was totally a honda & nissan man (because thats what sells) but 200k on an import car with an aluminum head isnt impressing me as much as 200K on a cast iron head american made car. Overheat the aluminum and see you at the machine shop.
Overheat the cast iron and chances are you will be ok.