I believe what you are asking is impossible to find. Gilbarco is still in business, so send them a request, possibly they will answer. According to my records G&B made 129,687 Model 996 gas pumps between 1948 and 1951. Possibly they kept a record of where these pumps went, but I doubt it.
I do know that Tokheim did keep a record of some type. When Tokheim closed around 2003, they had a big auction. Old literature was not a big item in the auction, so a small group of people in Ft. Wayne went together to preserve the literature. I got many of the duplicates and copies of the ones where there were only one item. I spent a great deal of time in Ft. Wayne going through a lot of the literature. One thing I was shown were what we might call a book style file. Each page was for a pump. It specified items about the pump, including the serial number. There were literally hundreds of these files. I believe they are now in the library at the Auburn Museum in Auburn, Indiana.
Now, if G&B kept such records, someone would have to sit an go through 129,687 records to find it information, if this type of record even has information as to where the pump first went.
G&B was and still is a very large corporation. While some very small pump companies advertised that you could "by pass the middle man, buy a new pump directly from us," G&B worked with distributers. These distributers would sell, then install and maintain the pumps they sold. These distributers are what we call service station equipment companies. Very large oil companies would also purchase pumps by the hundreds, they would specify how they wanted the pump painted and branded. Actually the pump companies kept these decals, etc. in stock for the large oil companies. I have about 1000 blue prints that came from the Bennett Pump Company, that explained how the pump was to be painted and branded. The blue prints even have the measurement as to how far above something the large company decal should be. My blue prints cover from around 1925 to 1940.
One more thing, when a dealer decided he needed a new pump, the old one was usually sold to a rebuilder. Every large area in the U.S. had a rebuilder and they sold pumps to each other. Today, many pump being found with 4 or 5 different decals on them from as many different companies who used the pump.
Again, I don't believe the pump companies keep this type of record.
Author, Gas Pump identification books, 1st and 2nd Editions. The new third edition is available at: www.gaspumpbible.com
Author, 1st and 2nd Editions. 2nd Edition is still available at: www.gaspumpbible.com