du I would drive it and not
worry about a rebuild until about 400k miles (as long as you do what is right in regards to oil changes). I recently purchased a 1985 300D with 218k miles and it starts and runs great. I replaced the timing chain and the first thing I did after that was put it up to 95 on the interstate. The engine runs out great at around 4k rpm (I was scared to do this not knowing the history of the timing chain). Don't spend the $ on the rebuild and get another mechanic to give you a second opinion if you still have doubts. The key thing (I think) is to look at the differences between the cylinders) and not necessarily the numbers.