I spent a good hour last night going through tons of pics on the PAK40 looking for refs on ammo boxes. I have concluded the large metal cases included in the newest Dragon kit were not used for this type of gun. I have only seen pics of the metal individual round cases and 2 or maybe possibly 3 types of wooden shipping crates and that's it.
Of course,I have learned to never say never where the Wehrmacht is concerned so any additional info would be most welcome.
TIA,
J

Don't know if you've seen these yet:
http://wehrmachts.kisten.free.fr/pak40.htm

and this one:
http://wehrmachts.kisten.free.fr/container_75mm_pak40.htm