if you are looking at a car and pondering if its an original cowl car, see if it has its matching numbers hood. It should have a number on it. It could make you feel more comfortable. There were not that many cowl hooded cars when you take out the copo production and the pace car totals out of the 10K hoods made. No docs will be a tough call. A correct date (week) matched hood would really help.
Here is a thread to decifer how to find the number:
http://www.camaros.org/forum/index.php?topic=3181.0