As I mentioned in an earlier post, I just completed a Tench-Guppy II, using the Lionfish/Growler kit. If there's anything I can help with, just ask, here, or contact me by Email at << mkeatingss@cox.net >>.
The main difference between the Gatos, Balaos and Tenchs was a thicker hull and the tank layout. Neither show up on the model. But keep in mind, also, that there is a small difference in length, Gato 307', Balao 311.7'. Tench 311.8' and the Tenchs were .1 feet wider in the beam than the Gato or Balao boats. That's a maximum of 0.3 inches in 1:192 scale, or 0.8 inches in 1:72 scale.
The 3"50cal, designed for these boats, was usually replaced with a 5"/25cal or a 4"/50cal, during construction.
If you're interested in subs, I highly recommend the "United States Naval Submarine Force Information Book" by Jim Christley, published by Graphic Enterprises of Marblehead in Marblehead, MA.
This information is brought to you by Plastic Modelers For A 1:72 Gato/Balao/Tench Kit (me). To join, you must write Revell, requesting the kit. And continuing to do so every six month until Revell a) Produces the model, b) Goes out of business, or c) Sends two large, Mafia goons to break your knees.
Mike