7 quarts is a nominal figure.
The sump Mike sold while there were still good cores around is a High Energy unit , and is ex Australian, and the Aussie engine had few differences when they went to hydraulic lifters, like a wider block, and a different part number for the 6750 coded dip stick. About 1964, a whole raft of changes were made to the 200 engine, and I guess they are quoting the Australian figure plus a couple of quarts.