Road King 2x12 Wiring

Hello,
Long time DC-5 user here, but recently bought a Road King 2x12 horizontal off a friend. Problem is, he took off the jack plate and disconnected the speakers. I got a new jack plate with three inputs, but have no idea how to wire it. My immediate assumption was to wire up all the positive and negative terminals together, and add wired to the third jack to bring the two 8ohm speakers to 4ohms in parallel. On second thought, this would just leave everything connected so no matter what jack you plug into it would be 4ohms.

Anyone ever had a look inside one of these? Is there some sort of circuit board connected to it? Can't seem to wrap my head around how it works. Any thoughts are appreciated!

There's got to be something to the isolated 1/4" jacks seen in photos... the plastic sleeve must be important in keeping the grounds isolated. If I can find them in the 'normally closed' position, that means they'll only be active when a cable is inserted, eliminating cross-talk. perhaps it goes like this: (i'll refer to the speakers and jacks as L, R, and Stereo) L speaker parallel to L jack, R speaker parallel to R jack. Stereo jack + to L, - to R. I think there's a jumper between L and R jacks, best guess is + to - .

Maybe if you use only the isolated jacks for all three, you could have two sets of wires coming from each speaker and just connect one pair to L one to R and both to the stereo jack. If they're all isolated, then you should be safe having the wires hit the jacks because the circuits will be closed.

Any of that sound right?