Hey , Nice start on your build , gm DID actually make a sports roof 69 impala what they considered a fastback lol , i used to own one , heres a pic of one , although not mine , i wish i still had mine...although not a fastback, the roof was different than the standard caprice/impala. mine was an original ss with 427 and turbo 400 bought it back in the 80s for a mere 600.00 enough rambling , im getting tears on my keyboard...your model looks GREAT so far!!