I know that on SBC and BBC where the motor code is on the pad up front by the water pump, that there is a series of #'s that is supposed to correspond to a sequence in the VIN # of the vehicle it came out of. Unfortunately, of all the hot rods i've ever owned throught the years, I don't think any of them ever had the original engine still in them for me to actually verify that was true. On the later 6's, I think there is also additional #'s on the distributor pad that also is supposed to have matching VIN #'s of the vehicle it came from. Maybe if you have an original engine from a car or truck you still own, you might check and see if any of those #'s seem to match any sequence of #'s on the VIN. I know that after 1960 or so Harleys and other motorcycles had stamped ID #'s on their engine cases to match the frames for theft identification, so Im sure the automakers had some similar method the keep track of their engines....
