look for indicators
My '62 is not an SS so I can't say for sure but you might give this a shot......if the inner bucket seat mounting brackets are welded to the floor and still have factory dum-dum (caulking) around the bracket edge to floor connection, and the console brackets are welded to the floor with the same dum-dum condition, and the grab bar mounting holes look factory punched out not drilled, then I think you could be highly confident it is an original SS.
'63 Impala SS 409/425 owned since '71
'64 Impala SS 327/300 factory 4sp p/s p/b air
'66 Impala 327/275 glide 2dr/hdtp
'66 Belair Wagon 283 700R4
'62 Impala 350/350 dual quad th350 2dr/hdtp
'00 Camaro SS 6sp hurst SLP