Van,
Do you think it is a Caprice because of the roof line? That appears to me to be an Impala SS427 Custom Coupe not a Caprice based on the rear emblem and lack of Caprice chrome. It is the rarest of the three body styles. It would be nice to see more pictures some day if you can. Here is what one looks like. The do not have much in the way of identifying markings denoting them as Impalas.
68 Custom Coupe
Rick