Original engine?
I've taken my vin number to dealer ships and they were able to look up specific parts in the vehicle. Some parts like the engine block or axles are stamped or have numbers forged on them. The stamps location very on the type of engine. I have a 5.8L and I believe its on the front passenger side of the block right below the head. You can compare the stamped numbers to the vin to match your parts and see if it whats rolled out of the factory.

