The 1996 RT/10 (pictured above) is considered to be a gen1 car like the 92-95 Vipers.
96 RT/10 had different suspension setup than the other gen1's and a rear exit exhaust but the engine is the same as in the older ones. It's rated to have 15 hp more because of the exhaust. So this one is rated at 415 hp.
96 GTS had the more powerful 450 hp gen2 engine. RT/10 didn't get the new engine until 97. In 97 RT/10 had the other gen2 updates as well like side windows, outside door handles and airbags.
The GTS style hood louvers came in 98.