I haven't cross-referenced them with the NP equipment, but I know that the
CB&Q built flatcars using a NP design that, at least generally, looks like
the models being discussed here. This is the class FM14 53'-6" straight
side sill fishbelly centersill flat 80200-29249 built at Galesburg and
92075-92349 at Havelock on the Q. During
1944 these were equipped with metal housings to carry B29 wing root fusalage
and nose sections to Martin-Marietta's Fort Cook, Nebraska B29 assembly
plant. The
housings were removed strarting in September 1945 when B29 production ceased
at the end of the war.
Presentation drawings of the FM14 with the housing were in Burlington
Bulletin No.15. IIRC I have some construction drawings on the cars in my
collection if anyone needs them.
Charlie Vlk