Well, I got everything working. It was a pain int he ass, but the truck runs.
I called Magnuson, and told the sales person I have a 2001 Chevrolet 2500 HD with 6.0V8, and that the stock fuel pump had died, and I wanted to put a Walbro 255LPH kit in. Well, they sent me a kit....the wrong kit. The 01 has an in tank fuel pump; they sent me an inline kit.
To make it work, I took the fuel pump assembly out, and removed the stock fuel pump. I then ran fuel line down the inside of the bucket to the bottom of the tank, and hooked it up to the stock fitting on the top of the stock fuel pump assembly. From there, I hooked up the Magnuson kit as instructed. Truck is running great.
I'm mildly pissed, because what I asked for, and thought I paid for, was a stock replacement/drop in piece. That's not even close to what I got.....