74 Dart engine wiring diagram
You need a 74 factory shop manual. 73 is similar but there IS differences, including the ignition interlock.
You can download a 73 manual from MyMopar (which came from the guys here)
and MyMopar also has "aftermarket" wiring diagrams. However, they don't show the seat belt interlock wiring, and leave out options
If you still have the interlock "box" (look for a small box under the hood with a reset button) Cut and splice the two yellow wires together
http://www.forabodiesonly.com/mopar/showthread.php?t=14304
I started to scan the 74 electrical but was happy with the results, and don't have it yet.
The thing is, starting in 73 and newer, the wiring is all chopped up in the diagrams. If you can post specific questions, we can waltz through it.
To get an idea of how this works, start with the 73 manual in the meantime.