What options are put on the Cowl Tag? From what I understand only the options that had to do with the body ie manual transmission, air, color interior. How would you know if your car originaly had power steering for example. that would not be on the cowl would it?

It depends on the year and the assembly plant and whether US-built or Canadian-built but you're correct in your assumption. The body plate generally would only show what trim-type options would be installed on the body or interior so preparations for that option could be made. Something like the rear antenna would alert the trim shop and the body shop that it was to be installed...trim shop had to ensure the longer cable was installed and the body shop had to know the hole was suppose to be there. Very few 'hard' items would be coded but things like trans type (auto vs manual), A/C, rear antenna, deluxe seat belts, etc. would be as they had some effect on the body prep.

Check here (http://www.chevellestuff.com/tech/trim_codes.htm) for some options listed on 64-67 body plates. Again, only certain assembly plants used these codes, Atlanta, Framingham, and Kansas City. Fremont did to a very limited extent and they would use the RPO code for the option.

For those plants that did NOT code the body plate, there are numbers on the plate that corresponded to paperwork with the car as assembly was done to indicate what was to be installed.