It depends on what you want to do. You are changing it from factory at this point, so its up to you where you want that change to be. My personal opinion is to leave the factory connectors alone, just use the adaptor. In the case that you are running your own wire to the speakers, splice into the metra harness and leave the dodge harness stock. Everything is better in the long run (repair wise) stock.
What I would do, is goto the door panel speakers where all the speaker hookups are, and bypass the amp. Using the wire in the door that originally went to the amp, just hook it straight to the speaker.
Ex. On the front left door. The wires coming from the radio for the front left door speaker, will be dark green+ and brown/red-. You would hook those two wires directly to your front left door speaker (splice in the front left tweeter as well, it will work just fine)
For the rear left speaker, you would take the brown/light blue- and brown/yellow+ in the front left door and splice them into the (4 Door) brown/light blue- and brown/yellow+ (2 Door) white/dark green- and white/violet+.
That way you don't dink around with the factory dash harness, and any time you want to remove your radio to sell the truck, you can go buy a cheap $40 bit with the adapter, and plug it right in no problem. Since you have the infinity system and are removing the amps, do not hook up the light green wire on the factory harness. Do not cut the factory harness, just cut the metra harness if it does infact power that wire. Otherwise the case may arise down the road that the now disconnected wire hanging in the door shorts to ground and blows the fuse.
