[husker boxster]

If you're trying to figure out the engine mileage for maintenance purposes, that's a waste of time. Since you're not allowed to view the actual maintenance, you'd have to assume the previous owners did scheduled maintenance and that's a pretty shaky assumption. As thstone points out, assume none of it has been done and start changing everything in some sort of order of importance and budget. With 50 or 90K on the engine, most wear items will probably be on their 1st or 2nd time needing replacement anyway.

If you're trying to find the mileage on the engine for conversation purposes, run a Carfax. Best case scenario it displays the date / mileage of the engine change. If not, it gives an ave mi / yr / owner. Since your replacement engine was built in 2004, estimate that it was put in your car in 2004 or 2005. Use the miles / yr and est the miles for those 2 yrs. That should put you in the ballpark.