71 duster all signal lights shorted

What you are claiming is mostly impossible. In other words you are missing something important, and probably a lot simpler
1....What did you mean, "tested around and cut all the wires?" Cut WHAT wires?
2....Just how did you determine that the "battery + and - are shorted together?"
3....Just how did you determine that the "bulbs are grounding?"

WHAT are you using to conclude all this?

SO.............

A...DO NOT use continuity/ ohms to test for grounding like this

B....If you believe the battery connection is shorted to ground, do this: Get a large wattage bulb, such as 1156/ 1157 and socket, and wire that from the battery NEG post to the battery NEG post clamp. This puts the lamp in SERIES with ground, so that if there is a short, the lamp will light brightly. Then you can "casually" go around and look for the short---remove fuses, disconnect components (and don't for get the alternator) The test lamp will protect the system from burning anything up

C....Is the car wired "stock" other than you eliminating the bulkhead connector? Are you reasonably sure you reconnected the wires through it the same as they had been?

D....What about the big red and the big black ammeter wires which have eyelets attaching those wires to the ammeter on the cluster? For testing, you must bolt or jumper them together and SAFELY insulate THEM FROM GROUND. BLACK is ALMOST NEVER GROUND and both those ammeter wires are ALWAYS HOT

E....If you seem to get nowhere, disconnect the alternator big wire from the stud and tape it, and pull all the fuses. See if your test/ safety lamp in the ground goes out. Make certain all switches, dome lights, etc, everything is switched "OFF."