1959 GM roofs

I am trying to fit R/M 1959 Impala with a 1959 Oldsmobile flat roof from the Modelhaus to make a 4DR sport sedan. Now the cars had different wheelbase lengths. I can hardly imagine the roofs had the same length. If they were all of the same size, how would the passengers enjoy higher comfort standards in a Cadillac by a larger wheel base while the head room is kept the same as in an Impala or a Catalina? Were the roofs oversized for the smaller classes (Imapala, Catalina,..etc.)?

The answer is twofold.With the real cars there was a difference in wheelbase between the corporate body designations.This was usually,but not always,ahead of the cowl.So there may or may not be a difference in roof length.With the model pieces,there was probably enough fudging of dimensions by the original mold makers(for aesthetic reasons)to render the scale difference insignificant.