Headlights on when battery is hooked

'Fraid so. If the dimmer has been cut, hard to say what was done. You can download a free '73 service manual at MyMopar, and there MIGHT be some differences between 73 and 74. One difference is that the 74 has the seat belt interlock. It might also help you to download the '72 manual, as the wiring diagrams are "shown" different. Up through 72, there were "line drawings" that is you could follow each wire from one place to 'other

In 73, this changed, to a completely different layout, which makes things harder to follow.

Also useful, are the separate wiring diagrams at MyMopar. These are often incomplete as to options, and sometimes leave out connectors, but they can be easier to follow