How do I find out?

70 Chevelles Vin tells where car was built. Mine was built in California. It will supply some info and decoders are avail on line. How about tracing previous owners titled through Motor Vehicle?

try bob's chevelle 1-866 243-8355 they have a historical service should be able to get you what you need.

do you even know if it's an SS ?

there is no tag on the firewall,check inside glove box.