It's a big-time, long shot of a stretch to possibly get your hands on this information, but a great resource would be finding the old records of a stationery store or other business that sold baseball cards in 1972. They would have records/ledgers of when their outfit received the shipments from Topps.
So, find a very old person who used to run a store and ask to rummage around in the boxes in their basement. Simple.
