The Viper kits out there are front calipers only. They are not a complete Viper swap and they are not available for the rear. The front rotors can be either the mid 70s factory 11.75" or a later model aftermarket 14".
What the conversion will gain you is a few pounds off each front corner, better ability to modulate brake pressure at speed, and, Like Brads70 pointed out, a greater range of pad selection to better match your driving style.