Through the magic of digital photography (ie. take a hundred pictures to ensure one good one) I have put together a collection which documents the numbers on my 1969 Z28. I call this set of pictures "Z28 By The Numbers". There always seems to be many questions regarding the engine VIN stamp. It took some work but I think I have a great picture showing this stamp. I've selected seven pictures which should be self-explanatory. Note the resolution of these pictures has been reduced quite a bit for this forum. I can email higher resolution pictures to anyone who requests via a camaros.net message.
ColoradoZ28

Nice car you have there Mark.

Ditto, very nice car with a perfect sitting stance.

2 minor corrections: :)
12437 on the tag just means coupe (could be L6 or V8)
X77 is not a 'base car'. It's a Z without style trim. Or in your wording: Special perf package without exterior style trim.