OK, say you have an all original 68 z/28, numbers matching etc, and 1 day your out driving it and 'wamo' something happens to the engine and the block is damaged, lets say beyond repair, what would you do? What if the block was repairable ie; crack repaired, cylinder sleeved etc., and you had to have it decked, what then? Restamp it? What if one of the cylinder heads got damaged beyond repair and you found a date coded matching cylinder head, and put that on the motor, would it still be 'original'? I have seen on E-Bay and other on-line sources where a seller claims that the car is all original and sells for big $$$ and then reviewing some of the pictures accompaning the ad you see a part you know is not original, that blows 'numbers matching' right out the window. Another point, what if someone 'upgrades' the internals of the motor ie; rods pistons, cam etc.?