Used Cars: Quick Question, compression results, compression test

Question
Hello,
    I am in the process of buying a used truck. It seems as though every older model truck I run into the motor has been "completely rebuilt",must be my lucky day...To come across so many trucks who's motor has been rebuilt : ). How can I tell if the motor has been rebuilt other than a compression test...any suggestions would help. Regards-Skyler
PS..I'm not even sure a compression test works either.

Answer
Well... you can't... If only internal parts were changed it will be very hard to tell if it has been rebuilt without ripping the motor apart to look. The gaskets will be newer looking, and if it was a complete rebuilt the parts on the outside of the block (distributor, alternator, etc..) would obviously look newer than the car is. A compression test won't really tell because an older motor can have good compression results without a rebuild. Generally a seller will say if it has been rebuilt (and if it has, get the receipt.. if it was really done they should have a receipt.. or give you the mechanics number atleast) - I don't like buying rebuilt things, because you never really know if it was done right... (talking to the mechanic that did it can usually answer that question though, but some people are good liars).