Change the output of the panel to detector reset. Then connect the 0v of your viper to it. This will power cycle the unit every time you set the alarm, thus clearing the led.
In the book of words
We've still got a load of Logic 4's and old Bentleys out there under maintenance, got a REALLY old ADE panel in our stores, boss wont let it go, cream metal cased thing with a KS, i'll have to grab a pic!
First system I installed myself was probably an Optima!