if you can confirm the engine is matching numbers via the VIN stamp on the R/H side of the pan pad (if its there), if it does match, go to the front left side of the block (small block) there is a Engine Identification Number stamped there which will give you the engine build date, the second last set of 4 digits are the 10,000 year calender. Now, the engine could have been built weeks before the car, my engine was built on the 12th December and the car was built on the 18th December,