I know of two sources on these:
Culotta, "Freight Cars Reference Manual", v 1, p 192
Masterson, Wagner, and Hoffman, RP CYC 12, pp 46-87 (see especially pp 78-83)
CB&Q class XA-14D (100 cars, 46650-46749) were built in the company shops in 1937-38. After Pearl Harbor, 60 of this class were rebuilt with 26" roof extensions, to carry wings and other parts for B-26 and B-29 bombers. The modified XA-14Ds were converted back to their original height during 1946. The Masterson article has two photos of CB&Q 46741 with its extended roof, and Culotta has a 1963 photo of the same car at its original height.
Al Brown, Melbourne, Fla.