hello david
 you are correct to their being both hard and soft top's on these trucks. i think there are pics on colin stevens' website showing both versions. the cwm has a 1937 ford prototype, and a hard top 1938 chev. i'm not aware of any surviving 1940 ford g/s which you mentioned, but hopefull one will turn up eventually.  i found this pic at the following link. 
http://www.army.dnd.ca/RCD/rcd/galle...worldwar_e.htm
thanks, and cheers!!
mike