The 235 in my truck has 58k original miles. It sat in a garage for about 15 years and was used very infrequently until I got it in 2003. It has a few oil leaks, but runs terrific. Nothing has been done to the engine except for regular maintainence. I have added HEI and dual exhaust if that counts. I'm not sure if any work was done to the head before I got it, but it seems to run just fine on unleaded. It doesn't smoke or burn oil and I can get up to 20mpg if I'm easy on the pedal(I usually get 16 - 17mpg). Even so, I'm replacing it with a warmed up and righteously built 261 in the coming months. I'm betting it will last longer than I.
