Maybe I wrong here, but I though that the PFE R-40-14
steel refrigerator cars built by PC&F just prior to the start
of the WWII had wood running boards, not steel open grid
type when delivered?

Jerry, the information about PFE came from the PFE book. The SP
switched to steel running boards for ALL house cars in 1940 and
never looked back. The numbers I quoted you were for those cars.
SP bought two groups of 1937 AAR box cars in 1937-1939 (-18 and
-19) that came with wood running boards. Most were converted to
steel by the late 50's, if photos are any guide.

Perhaps Tony Thompson can help us here,
also it might be interesting to find out how may wood running
board SP 1937 AAR steel box cars delivered prior to the war
and 1940 were also delivered with wood running boards?