Easiest tap for electric gauges - 1974 duster

What's wrong with getting a shop manual and doing it right?

If you don't mind the gauges being on in both "run" and "accessory" you can tap into the fuse panel. If you want them on "run" only, tap into the fuse at top left, or get into the cluster wiring where they were originally supplied. Look at the bottom two diagrams. The second from bottom is the PC board connector. "G5-20 DBL" is the incoming ignition feed powering the cluster. This is switched 12V "ignition run" from the ignition switch.