AHM Heavyweight: 12-1 sleeper = Pullman; Observation and Combine = ATSF; Diner = Southern; Duplex Sleeper = Pullman, for PRR; RPO and Baggage = close to B&O, though not exact; coach = Southern??
AHM Smooth Side: RPO, 10-6 sleeper, duplex sleeper, Observation = PRR; Dome and Diner = UP.
Mmm - didn’t I see this same question posted by the same poster (with some pretty good answers) over in the prototype forum about a week ago ? http://cs.trains.com/TRCCS/forums/t/182848.aspx
One thing I’d mention from that link is that the person who posted it is apparently more familiar with postwar streamlined cars than heavyweights. Regarding the Athearn ones, the majority of heavyweight RPO’s and Baggage cars were less than 80’, normally in the 60’-70’ range. Coaches were also often around 70’ feet…don’t know if anyone ever counted, but I wouldn’t be surprised if the majority of heavyweight coaches were less than 80’ in length. It wasn’t until the lightweight streamliner cars started coming out from Budd and Pullman that all cars tended to be 80’ long.
The length of a passenger car was not always measured consistently in prototype documentation. It may be the total length over coupler faces, but sometimes it would be the length of the passenger section. So you might have a nominal 70’ car but by the time you add in vestibules at each end it is actually 80’ long. Just another headache for modelers and historians when researching the prototype.
I would be surprised if there were more than a handful of heavyweights designed for long distance trains that were shorter than 80’. Commuter cars may be different, since shorter cars provide more doors in a given length for faster loading and unloading, even though more cars are required. Head-end cars did come in both full length and shorter versions.