There was an article on kitbashing these cars in styrene in an old RMJ. It used the Walthers (formerly Golden Spike) 50' plug door boxcar flat kit as a starting point. New roof and ends as I recall. The result is a car with 12 panels and what appears to be the proper sill, and with a "close" space for the door (the seams are a little too far apart for a 6' door to fit just right. Nothing about the proper underframe.
