4th Gen JBL wire harness help needed

[Sandraqu]

Tapping into existing amplifier harness

Rather than cutting wires, or running wires from the head unit, I intend to tap into the existing amplifier harness. I have ordered spade blade crimp wire connectors

I have also ordered a Metra 70-8117 harness, but I'm not sure if that connects to the amplifier harness at the rear of the truck. I will update the thread when I know this information.

Based on the wiring diagram information provided in this thread (thank you [MENTION=97200]Rhoov1[/MENTION] for the wiring diagram) I can get most of the audio I need, but I have some questions. Please note my head unit, door and sub audio system is aftermarket. I am trying to connect an aftermarket amp.

My main question regards the RCA inputs. I can run them from an aftermarket head unit, but I'm wondering if I can tap into the wiring harness at the rear of the truck with a speaker wire to RCA connector

Question: Is this an RCA input on the JBL Amplifier Wiring Harness?
- Pin 2 Left Input -
- Pin 3 Left Input +

Copy of image for convenience. I hope it displays.
http://uploads.tapatalk-cdn.com/20151023/867af034663156e9628824b9a50a36f3.jpg

These speaker outputs I can run from a 5-channel amp

- Pin 28 L/R (Left Rear) Door Speaker +
- Pin 37 L/R (Left Rear) Door Speaker -

- Pin 29 R/R (Right Rear) Door Speaker +
- Pin 38 R/R (Right Rear) Door Speaker -

- Pin 30 Left Front Speaker +
- Pin 41 Left Front Speaker -

- Pin 31 Right Front Speaker +
- Pin 42 Right Front Speaker -

I would run the 2 Ohm Sub in series for a 4 Ohm load
- Pin 32 Sub Coil 1 + <-goes to-> Pin 44 Sub Coil 2 -
- Pin 33 Sub Coil 2 +
- Pin 43 Sub Coil 1 -


Center Speaker I can run from the head unit 50W at 4 Ohm.
Question: Is the Center Speaker 4 Ohm or 2 Ohm?

Rear Pillar Speakers stock wires are run in parallel.
Question: Are they 4 Ohm in parallel to 2 Ohm, or 2 Ohm in parallel to 1 Ohm?