He might be looking for the RFB (?? can't remember if that's the correct one ??) version, where they held 4 extra torps in the forward room, as compared with the Gato... ?? From Wikipedia, partial stats (oh so reliable):
Gato
Endurance:
48 hours at 2 knots (3.7 km/h) submerged[3]
75 days on patrol
Test depth: 300 ft (90 m)[3]
Complement: 6 officers, 54 enlisted men[3]
Armament:
10 × 21-inch (533 mm) torpedo tubes
6 forward, 4 aft
24 torpedoes[4]
1 × 3-inch (76 mm) / 50 caliber deck gun[4]
Bofors 40 mm and Oerlikon 20 mm cannon
Tench
Endurance:
48 hours at 2 knots (3.7 km/h) submerged[4]
75 days on patrol
Test depth: 400 ft (120 m)[4]
Complement: 10 officers, 71 enlisted[4]
Armament:
10 × 21-inch (533 mm) torpedo tubes
6 forward, 4 aft)
28 torpedoes[6]
1 × 5-inch (127 mm) / 25 caliber deck gun[6]
Bofors 40 mm and Oerlikon 20 mm cannon[2][4][7]