Aftermaket dash speakers without cutting the factory harness
 

So Crutchfield sells a harness, Item# 12071042, for the dash speaker. It does not work. It fits the plug that goes to the 3.5 inch speaker but it doesn't work because the sound has to travel through the tweeter plug to get to the 3.5 inch speaker. No idea why they wired it that way.
I was about to splice the wire when I came up with this idea, that worked. I had some 14 gauge house wires laying around. I cut the ground wire into small pieces and bent them into a small horse shoe shape. Then I flattened them out with a hammer. I used them to bypass the tweeter plug so the sound can travel to the 3.5 harness, and then I used the harness from Crutchfield. Hopefully this picture can explain what I did better than I can.

Any issues with this yet? How's it working for you?

No problems at all.

I am little confused as how the those "horse shoes" will fit the wire harness?

Bringing this back up from the dead... but if anyone wants a quicker solution to this, spade connectors will also work nicely. Just slot them in and secure with tape.

https://media.rs-online.com/t_large/F0534632-01.jpg