Check out Directed Electronics . They make the Viper (I am happy with it) but also the types that wire into the stock system. Also, check out this sytem, DEI's Hornet System, connects to your present RKE and uses your existing remote...

Good luck

"My Name is Richard. I am a Contouraholic."
1999 SE Sport Duratec ATX Spruce Green; Drop--In K&N Filter; VentShades;
Fog Lamp Fix Mod & PIAA510s with Bumper Braces & Stock Type aiming screw mod;
PIAA 9006 Super White Headlamps
AIWA CDC-MP3 HU; WeatherTech Mats
Viper 600ESP w/Remote entry