Hi Colin,
Are you after info on the 1A2 or 1B2 FFW type bodies ? The 1A2 is the first type , it is shorter , with external stowage boxes , it was in use with the 1940 cab 11 models and also seen on some cab 12 vehicles . The later version , 1B2 , is longer and has internal stowage for the chorehorse etc.
It appears that the 1A2 body was designed for use with a No. 11 wireless set , these sets were a UK set, designed in late 1930's , also made in Canada and Australia . Basically the 1A2 is a copy of the British PU style body , the wireless fitments are very similar .
The later style 1B2 body, was designed with a No. 19 set in mind . In actual service , various radio sets would have been installed , depending on what army, what was available etc. In the M.E., a whole mixture of sets was in use , British, Australian , Sth African , N.Z., signals units all had their own sets .
This link to my 8 cwt article may help you out .
http://www.geocities.com/vmvc1au/8cwttwins.html
Mike