Found my dads original 1971 duster!

Nothing so far screams gages failed.
You all connected a "12 V" power source to the key switch feed. Pretty much the same as would be normal.
Nothing else is needed to start.
Where is the other half of that cut wire J1 ?
Even if it the car battery was disconnecte,the main splice would get energized by the alternator once the engine was running. If the other half of J1 touched ground => smoke.