Prob with 2000 C3500 5.7L fuel pumps.

SOURCE: need a wiring diagram for

I have found the wiring diagrams online to be unreliable -- they sometimes are listed under the wrong model or year, and have often caused me a lot of frustration and confusion. It is possible that you can get one, but for the sake of reliability you should probably pick up a Haynes manual for your truck - - it will have all of the diagrams you are looking for, as well as many other useful bits of information for repairing your truck. You might have more luck finding the diagram than I ever did ... but I still recommend picking up a Haynes manual for your future reference -- at under $30 US it can save you thousands in mechanic costs (if you have the time and tools to do your own repairs). These manuals are available at most auto-parts stores and larger bookstore chains.
If you are unable to find the Haynes manual for your truck, or just have your mind set on getting one online, you should include a bit more information to assist with your search:
1. Make, Model and year of your truck (which is here) 2. Engine size / type (is it a diesel, turbo-diesel, hemi, standard 5.7 L gasoline engine?) 3. Are there any engine or other upgrades that could affect the wiring? 4. Is it your entire wiring harness that needs replacing, or just the fuel gauge wiring? 5. Does the truck have an automatic or a manual transmission? (this can affect the wiring harness style and connections). 6. Do you know why the wiring burned out in the first place? (so you can possibly avoid the same issue in the future by changing where the wires sit when connected is possible)
I wish you the best of luck ... if you can't find the Haynes manual, please reply with the above information and I will do my best to help you find the appropriate wiring diagrams for your truck.