block vin is 1000 off

[DSYenko]

I have a friend that recently purchased a 68 RS/SS Camaro. 325/396 and the car is pretty darn original other than 1 repaint with 90 plus thousand miles on it.The wierd thing is the engine is supposed to be factory original with this body but the vin is exacly 1000 off the vin in the dash. What im saying is the 4th digit from the right going back left is one number higer or lower depending on if your looking at the vin in the dash or the engine pad. I am just short of positive it's the correct motor for the car.Is this something that did happen out of the factory once in a while? Thanks guys