Don't quote me on this, but I thought that these cars were made to haul two 35' trailers, which were the largest on the road at that time (1955). I also thought these were sold to Trailer Train with its inception. That was probably a good thing for the PRR since 40' trailers came to be not too many years after these were sold. The 40' trailer rendered these cars somewhat useless since they could haul only one. I remember seeing some of these F39's in the late 80's on Conrail in storage. They were in the MTTX (general use) trailer train scheme. All of this is based on my own recollections of articles and my own observations. I thought someone did an article on these cars since Walthers (again, I think) brought these out in HO many years ago. It was in RMJ or MRing. I hope this helps.
