That "pad" you're looking for is actually part of the BLOCK DECK in front of the passenger side head (I wasn't sure if that was clear on the previous post). It's often covered with grease & dirt and tucked behind and under the alternator. Kinda hard to read even if you know exactly what you're looking for.
There will actally be two series of numbers, one will have a code for WHERE/WHEN it was built, the other should (as he said before)be the last 6 numbers of your VIN followed by a 2 letter suffix code (went to 3 in 1970) that would tell what size engine, type of transmission, even SOME options like AC or Smog equipment, many are "model specific" ie: Camaro, Fullsize, Chevy II etc.
There are various levels "#s matching" depending on how far you want to go with it (Vette people are real freaks about this stuff). There are numbers on the Trans, distributor, carb, rear end, etc., etc., etc. that can be traced to a specific type, time, and place, and often to the original car installation.
All this is only of any REAL importance if you're trying to document/justify a High Dollar allegedly rare/unique vehicle during a sale or in judging. An original Matching #s car IS worth more, but I question the desire to trade the FUN of owning a Camaro for the Competion/Pedigree/Money thing. Besides you can't be lulled into a false sense of security because there are a number of unethical folks out there who are more than willing to create whatever "matching #s" car you want or they think they can get a good dollar for.