For clarity, I think the SS427 was not a model yet for the 1966 year? RPO Z-24. All 66 Impala's with the SS and 427ci were Impala SS's with the 427 (I know a small distinction).
That being said, couldn't you get the L72 in 66? Which 427 it has would make a difference in value I would think.
Would look something like this:
Rich