Keep it at 6V and wire the two motors in parallel (+ of the existing motor also goes to + of new motor; likewise with -).
Note that the peak current draw will now be 2x, which may be marginal with existing wiring and/or may stress the battery.
Yes, bigfoot, or any of the early Metal Frame jeep[…]
wire harness connector for escalade shifter ass[…]
Nice! Looking to follow suit. Any chance you could[…]