The only difference I have seen in a cross sill is when the truck came with an inside frame rail gas tank. There is an indentation for the tank on one of the cross sills. Those tanks were only found on Carry-alls and Panel trucks, to my knowledge. Yours should all be the same.
My first reply was about the location of the sill along the rail. My original bed came with 3 bolts on each side with no cross sills, instead of the six frame bolts and cross sills, as mentioned above, I found on my parts truck.
