Viper 500, 2 Varad Super Bright LEDs?

Assuming that the Viper 500 has it's own LED output plug that's designed to connect to the LED that comes with the alarm, most likely that output is current limited meaning there is an internal Resistor.  In that way, they can use a standard LED (2-3 volt) and not have to use any resistors at the LED end.  Now these super bright LED's that you got,  are they designed to be connected to 12v or are they just plain LED's?   If they are designed for 12v, then they have an internal resistor.   Now driving two LED's from a current limited LED output may give insufficient current for those LED's to be bright.   Personally I would modify the alarm brain to give me a better output, but this would most likely void the warranty.    As far as both LED lead outputs being positive,  that doesn't make sense unless the use a special LED that is 2-color-reverse-polarity.  Then you would see positive on both sides from alternatively, but not at the same time.