Do yourself a big favor. Get yourself a reprint or original factory service manual, which are available here and there on CD. The manual for a 73 is available free over at MyMopar, but there are significant wiring differences between 73 and 74
Also bypass the seat belt interlock. Look under the hood near the fender apron or firewall lfor a small box with a reset button. There should be two "yellowish" wires. Splice those together
Here:
1974 duster seat belt interlock module removal
