Another possibility is that the blocks are the same and the mounting locations on the frames for those wooden blocks are different.
Here's another aspect of this question that has not been addressed. It might be possible within the same year to mount a pickup cab on a panel-body frame but is it possible in the same year to mount a panel body on a pickup frame? I'll check this tomorrow (on a 54 pickup and suburban) but I think there are added parts on the rear of the frame for the panel-body mounting blocks. I am not referring to the added gussets on at least one of the panel-body-frame cross members.
