fusible links?

I have a 74 duster with a slant 6 of course. I went to start it and it was running really rough. I turn on the light and they came on and flickered then both went out. upon turning it off checking the fuses and battery connections, I went to restart it and i have nothing. no turning over or anything. the only way it will turn over is if a use a jumper wire on the starter.I have power to two of the fuses. I was wondering if anyone else has had this problem, and if they know what it was. I was suspecting a fusible link. I checked the one next to the main wiring harness bulkhead on the firewall and I had power on both sides. If anyone knew where the other one is my manual says ther is two. Thanks for any input you have