If you have a streetcar and not a full blown gutted drag car, some wiring is tricky and using whats already there is sometimes easier and cleaner. Here I cover the basics on how I did mine which is a 99 model and the wires I used out of the factory body harness.
I forgot to add in the video, if the ohm settings for the fuel gauge doesn't work and you have a 99-later gm, try using 0-99 on the ohms side.
Revesion Raceworks gauge insert:
https://reversionraceworks.com/chevy/f-body/