Greetings,
The first conversion set (that I've seen) for the Revell Gato is out thanks to Nautilus Models. It converts the Cobia into the USS Batfish SS310. Includes deck, replacement tower, 5" gun, and some photo etch. What isn't clear from the initial photos is if they are including the SD Radar mast although there seems to be a hole in the deck for mounting it. Some of the bridge detail could be stronger such as the Target Bearing Transmitter (T.B.T.). It looks like you can build the tower a few different ways with different deck guns.
It looks a little different from the boat currently on display. It would be nice to get some feedback from the folks at Nautilus to speak more about the kit and what period in time it represents. Here are links to Nautilus and also to the USS Batfish web site which has a lot of information.
http://www.ussbatfish.com/batfish-main.html
http://nautilusmodels.com/
Check it out.
Dave