The 1974 models came with the dreaded Federally mandated " Starter/seat belt interlock system". This prevented the car from being started unless the seat belts were connected. The system includes many electrical parts that earlier cars did not have including but not limited to: Sensors in the front seat cushion to detect an occupant or occupants, sensors in the female seat belt latch, wiring for these sensors, a small 1" x 3"x 4.5" plastic "brain" that houses a small circuit board (Mounted behing the guage panel) and a small relay mounted on the fender apron near the windshield washer jug.
When the fusible link burned it probably sent heat through the wiring and damaged the wires associated with the seatbelt system. I had this happen to me on a 74 Duster. I ended up bypassing the seatbelt system entirely. I also went ahead and tied the red and black guage wires together and ran a separate 10g wire from the alternator directly to the battery positive terminal. The car then started and ran fine, though the ALT guage was stuck dead center at all times.
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https://board.moparts.org/ubbthreads/show...=17#Post6633732