I have the kit but have not built it yet. I'm still working on my Revell 1/178. I'll take a quick look at the Trumpeter and see if there are any gotchas.
It was only the first six Gatos that had anchor pockets on both sides. The yards were not able to get two sets of anchor equipment installed under the superstructure so one of the pockets was covered up before the boat was commissioned.
Squadron has two good books on WWII Fleet submarines. The FD DVD is a must. The book on the USS Cod is also a good reference for late war Gato boats.
Late war Gatos did not have as much railing as they did when they were comissioned. It was concentrated around the fairwater. From the gun decks fore and aft there was no railing. Also, the radio antennas were quite different late in the war and did not run the full length of the boat.
Since each boat became as unique in appearance as your fingerprint it is best to pick one boat that has good documentation and build to that boat. By 1944-45 there was no "generic" Fleetboat.
Here's my biblography of references:
Alden, John D., The Fleet Submarine in the U.S. Navy, 1979, United States Naval Institute, ISBN: 0-87021-187-0
Friedman, Norman, U.S. Submarines through 1945, 1995, United States Naval Institute, ISBN: 1-55750-263-3
Stern, Robert C., U.S. Subs in Action #2, 1983, Squadron/Signal Publications, ISBN: 0-89747-085-0
Stern, Robert C., Gato-Class Submarines in Action #28, 2006, Squadron/Signal Publications, ISBN: 0-89747-509-7
The Fleet Type Submarine, NAVPERS 16160, June 1946, www.Periscope.com
, ISBN: 1-4116-7753-6
Fleet Submarines of World War Two, 1988, The Floating Drydock, ISBN: 0-933126-72-7
Plan Book, Gato & Balo Class Submarines, 1990, The Floating Drydock, ISBN: 0-944055-06-0
U.S.S. Cod, Photo Museum Guide, 1999, Oxford Museum Press, Inc., ISBN: 1-930127-01-4