erik's linked photo also clearly gives evidence that no Harpoons were shipped at that time, though it appear that the ship was, indeed fitted for them. So, remove the canisters and only show the pads and possibly, again, the latticed launcher supports.
The system wasn't in service until two years later (1977). Of course Mk 71 was cancelled before fitting to any Spruances in 1978, so perhaps a 1980 (or so) fit would make more sense.
Too bad the Mk71 was cancelled. The Spruances might have been in service a little longer for shore bombardment use.
Unlikely, the hulls were not exactly lightly used by the time the Spruances were retired. And (as my head repeatedly makes sweet sweet love to my desk) NGFS is simply not a sufficiently important mission to justify entire ships with no other useful purpose. Not that Spruance wasn't good at other things, but it's a redundant capability considering the cost.