I would look on websites that specialize in chevrolet.Chevrolet forums would also be a good ppace to look.If the internet is not somewhere you want to look then I would go to your nearest chevrolet dealer for the information that you need.The last place i would look would be in chevrolet themed magazines
You can either try finding a engine book with all the codes listed in it. Otherwise you can just do a search online for "Chevrolet engine casting numbers". That should give you a bunch of pages that list this information.
The engine codes are in the car computer,the ECU so the only way to get them is via a scan tool
OBD1 or OBD 11 depending on car model/year. This scan tool will tell the engine error.
Go to nastyz28 if you are looking for V-8 codes. The codes are associated with the vin numbers for performance. Now if you are looking for engine repair light codes engine-light-help. I wasn't sure which one you were looking for. Hopefully either one will help you get what you are looking for.
At your locale chevy dealer. They will have all the codes you need and them some .Make sure you ask for the right one .Even at your locale auto parts store