So the motor is history. A date code then is only important to someone that has bought into the 4 week or so thing before the build. There is only one VIN to One Block. So if your motor is history why not build a stroker motor. No one will know unless they crawl under your car with a mirror and look at the casting numbers and dates. You can build at least 500ci out of a Low Block big block by using the 400 block and a stroked crank. There are many smaller CI motors under 500 CI that can be built by using a 383 block or a 400 block. No one will know when your ahead of him on the drag strip or street. If you want a 383 near your build date you might also be buying someone elses original motor.