When the E7 units were introduced to the Milwaukee Road in 1946, they would have first pulled the rib sided Hiawatha cars introduced a decade earlier. Lionel's 2006 Hiawatha cars 6-29191, -96 and -99 depict those.
However, in 1947, the E7s would have begun hauling the railroad's new Hiawatha cars, the ones designed by Brooks Stevens that included the Skytop Lounges. Those are depicted in the 21-inch aluminum cars sold by K-Line about 15 years ago.