Man, not too sure on how to help you. I was hooking up an older Alpine alarm myself, and had a lot of questions on the door locks. They still aren't correct, but they kind of work... Here's a website that may help:
http://www.the12volt.com/. I did a search on
www.google.com for alarm installing, and found a couple other good ones, but this one is by far the best.
Here's the wiring diagram for your truck:
2000 Dodge Ram Pickup Security Information
Constant 12V+ Pink/Black or Red Ignition Switch Harness
Starter Yellow or Blue/Yellow Ignition Switch Harness, Must Add Relay for Remote Start
Ignition Dark Blue Ignition Switch Harness
Ignition 2 Black/White Ignition Switch Harness
Accessory Black/White Ignition Switch Harness
Tach Black/Gray PCM Passenger's Rear of Engine on Firewall
Neutral Safety Wire Black/White (-) Ignition Switch Harness
Brake Switch White/Tan Brake Switch or Ignition Switch Harness
Trunk Pin n/a
Parking Lights Black/Yellow (+) Driver's Kick Panel White Connector Driver's Kick Panel
Head Lamp Pink/Red Light Switch
Factory Disarm Light Green/Orange (-) Driver's Kick Panel 1500 Ohm
Door Trigger Yellow (-) Driver's Kick Panel White Connector Driver's Kick
Door Lock Orange/Purple (REV) 10 Pin Connector Driver's Kick Panel Reverse Polarity
Door Unlock Pink/Purple Driver's Kick Panel
Driver's Lock Orange/Black Left Kick Panel
Driver's Unlock Pink/Black Left Kick Panel
Passenger Unlock Pink/Purple Left Kick Panel
Horn Wire Black/Red (-) 74 Pin Connector behind Driver's Dash
Windows Up LF=Light Blue, RF=Brown/White
Windows Down LF=White, RF=Purple/White
I hope that this helps in some way, shape, or form. If you have a Dodge manual, or even a Chilton's or Haynes, it should show the color of wire going to the LP. I would think if the starter and both ignition wires are hooked up properly, you should be getting juice to the LP. I would suggest taking taking a voltmeter and start testing which wires send a 12v signal to the LP when the ignition is kicked on by the alarm. I don't know how the wiring is routed on the automatics, but one would think it ran off the ignition #1 wire. I will look into my Haynes book tonight and see if I can come up with something more for you.