Back in the 80's my 340 Duster just died. I had all my accessories including lights and could not jump start it. I towed it home and found a large red wire that went from the firewall towards the starter that had a larger diameter in the middle of it. The wire was fatter for an inch or so from what I remember. I believe I was told this was a fusable link back then. It looked burnt. I spliced in another piece of the same gage wire and it started right up.
I don't know if this helps or not but it fixed my problem back then.