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There are no rules for it currently but I'm definitely going to have a truck with a naval harpoon gun in the flatbed.
Harpoons and similar rules for Max 34 came out in either Wargames Illustrated or Wargames Soldiers and Strategy. But yes, the Grand Tour supplement with have some extra goodies and weirdness ( such as Motorcycle Chariots)
Motorcycle chariots? Woohoo!!!!!