The Weaver wagon top box and express cars are indeed correct for 1:48 scale.
They were made using original B&O engineering drawings for them.
And yes, these cars are somewhat narrower than 10' wide overall, which most other freight cars are. They were 9' 9 5/8" wide over their sideposts with a 9' 2" clear inside width. The wagontop box cars also stood 14' 5 7/8" high, rail to running board.
The slightly narrower width and rounded eaves on thse cars with their 10' interior height was purposefully done to maximize their cubic capacity and also assure their fit through B&O's old 1840s era tunnels.
B&O had to watch incoming cars from other roads carefully and route them to assure they would not run into a problem with clearances in the older tunnels. The railroad produced a clearance booklet which descibed the maximum dimensions for cars permitted on each line and branch track.
Box cars having a 10' 6" interior height had to be re-routed to avoid the older tunnels until the mid to late 1950s. That's when some older tuinnels were 'daylighted" by removing their overburden, or their roadbeds sunk to lower them and gain clerance for taller cars. 1840s tunnels were also rather narrow. So double tracked tunnels became single track until another track could be built around the tunnel, or a second tunnel dug for a second track.
Also to note; mill gondolas of 65' in length were also narrower in overall extreme
width at about 9' or so. This was to assure their clearance on relatively tight curves and in the close confines of industrial trackage.
So in true 1:48 scale, not all modeled cars would be of equal width. Neither were their prototypes!
