restamped engine block

[qksilver]

Was at a swap meet yesterday and looked at truck, not seriously just curious.
It was a 67 cst fully loaded. The owner said he had the engine completely rebuilt including having the engine decked. I looked at the engine and it still had the engine I.D. # on it.
I thought when an engine was decked the # was machined off. The owner seemed at little shakey, the suposed 67 had a 69-72 cab (foot emergency brake).
Plus a few other little things. He did have the machine work done at a good local shop and the receipt broke down all the work.
Do they restamp engine I.D. #?
Didn't have my camera otherwise I would have taken a pix.
Thanks,
Steve