The cowl tag just says V-8 or in-line six the engine ID code has the application. If you were attempting to clone a big block car you start with one that has most all of the castings within 4 days of the build week.
Oh you mean you want things like an engine code of ID for a 425 horse manual secondary 427 in a 1966 passenger car with a four speed? There are 14 different codes depending upon horse power of the engine, carburetor on top, and tranny it was mated to; and other such things such as being A.I.R. equipped if being shipped to California. They can all be found on page 42 of Alan L. Covin's Chevrolet by the Numbers for 1965-'69.