[Elijah]

I just used a simple voltage tester, the kind where you ground it somewhere on vehicle with those little clamps with teeth and it has a light on the end of a screwdriver looking deal, the light just turns on whenever there is current. One by one I tested all the wires that come from vehicle before it goes to converter box and wrote down which wire was right signal, left signal, brake, etc. Your new converter should have it labeled already on the wires, so that end is easy. Then just color match on the 4 pin end. Regarding the ground, you are right. Just needs a good ground, I just cut the OEM white ground in your pic where the box is and spliced it into the new white wire coming off the new converter. For some weird reason my brain struggles with understanding electrical stuff, so at first it seemed a little overwhelming me. I took it slow and double checked all the wires I spliced into and made sure the lights at the 4 pin connector were getting juice.
Hijack: BTW, I love the DIY black pearl emblems. I hate the gold ones on ours. Are yours still holding up well?