Look on virtually every Mustang and follow the black wires from the two bolts attached to the radiator core support. These go around the battery and end at the round single pin connector.
Of the two wires that have been grounded at the strut tower one would go to the battery negative. The other would go to the radiator core support ground buss.
Another option is to search car-part.com to search salvage yards in your area. Perhaps get a set of salvage yard battery cables.
Thanks for the info. I have a Pick N Pull and a U Part It near me I will go try. They have several new edge Mustangs. All V6s but I assume the battery harness is the same.
Sorry to resurrect an older thread but i wanted to ask a follow up question. These battery cables, if i were to go get them at a salvage yard, are they solid cables that go all the way to the starter or do they have a disconnect somewhere between the starter and the battery? I ask cause i have long tube headers and that starter is a royal pain to get to. Also are the GT and V6 cables the same?