I collect the old butterfly hood GMCs.

https://plus.google.com/u/1/photos/photo/112636930370126476644/6191993835626873602?icm=false

The front sheet metal is the same from 450 through 600. The cab is the same as a pickup except for the 5 window. They used a big window cab and put in a divider for the corner glass. The corner glass is very difficult to find if you break one.