Ok, the puter is the black box that is just slightly to the passenger side on the firewall when you are looking at the truck. You'll see a mass of wires coming out of it and running to the right. It may be taped up and you'll have to peel some of that back to find your wire. The color stays consistant. Once you find that wire, just confirm that it is the right one by checking the number in the wire harness that plugs into the puter. The harness has all the numbers on it, you may need a flashlight thought to actually notice them.
The main power diatribution box is between the brake booster and starter relay. It's a black box that has the main relays for your truck. IIRC there are two teminals that are connected to the outside of it. One of them is a single wire that is the color you are looking for. It's called the test tach terminal. It is the one on the side of the distritution box (the other one is in the front). I just spliced in there right before the terminal.
I can take a pic for you and e-mail it if you are still are unsure of the connection.
James