1st gen calipers are 2002 and earlier. 2nd gen are 2003 and later. I have never looked closely at a 2nd gen caliper to physically notice the differences, but I think they mount differently. One is not preferable over the other that I'm aware of, but the hardcore Viper guys may not share that opinion.
For pads, you can get a wide selection at the local parts house, Summit, Jegs, or any performance supplier. Just a quick search on Summit turned up 18 different pad choices for a '94 Viper, compared to 5 for a '79 Cordoba. EBC, Hawke, Performance Friction, Wagner, and more all make pads in differing compounds. The local dodge dealer ma be able to offer some selections as well.