The reason I ask is twofold:
You ought to take a look at this: http://home.pcmagic.net/bertfam/camaro.htm
and contact Bertfam (Ed).
Also, some suppliers advertise SS caps that really aren't the right one for a particular year. (Like the SS 350 cap that is often advertized for 67 - 68, but then they will disclaim it as original in the fine print for 68.) That RS cap may have been put on your car from "bad" information. It happens all the time and sometimes from what you might think is a reliable source.
Sounds like a sweet car... post us a picture!