Elliot Courtney wrote:
"I have two 4600 series cars (double sheath with wood door) and one 4300 series car (single sheath with wood door)."
The Accurail 4600 series kits model the USRA double-sheathed boxcar. The roads with the most numerous USRA DS boxcars in 1950 were Great Northern (1413 cars) and Rock Island (1153 cars). Decals are available from Westerfield. I uploaded a summary of USRA boxcars to the Files section in 2006 - it's been moved to the groups.io site and can be found by doing a search on "USRA DS".
The 4300 series kit is a 9 ft IH car with wood door and 7/8 Murphy steel ends. The fishbelly center sills in the kit can be replaced with straight center sills fabricated from strip styrene to model more prototypes. Possible prototypes or close stand-ins in service in 1950 are CN and M-K-T. This model can also serve as a stand-in for shorter cars - CNJ (8 ft 2 in IH); MEC (8 ft 6 in IH); CB&Q/C&S/FW&D, CNW (8 ft 7 in IH), though the difference in height from the prototype is definitely noticeable.