The "ground" wire connector. The trigger/motor connector. The spoolgun conductor block connector.

On the side opposite the supply, I mounted the three connectors used by the spoolgun itself.1. If I did this again, I would just use another SB175 connector, instead of the single PP120 connector. The reason being that the internal copper contacts for the PP120as the contacts for the SB175, which meant I had to grind down the contact to make it fit. The connector is called the "ground", but it does not always carry a negative charge. With flux-cored wire, the "ground" cable is actually carrying a positive charge, while the spoolgun tip is carrying a negative charge. With non-flux-cored [Mig] wire, using a shield gas, the polarity is reversed. We'll cover this more when I show you the internal wiring. I mounted the PP120 by drilling a round hole just large enough to squeeze the PP120 through, then sealed the whole thing with Sugru™.2. The trigger/motor connector mounts through a small round hole drilled into the sidewall, which is then secured with some self-tapping screws. I would use a bolt with a smaller head if I did this again.3. I'll cover the conductor block in more detail in the next step, but you'll want to cut the hole in the side wall a good bit larger than the size of the conductor block hole. I recommend isolating the conductor block so that it's not making contact with the toolbox's metal side wall. I tried mounting the block a couple of different ways before I found one I liked; the easiest way being to make the hole in the side wall a few sizes larger then the conductor block,and then use rubber washers and electrical tape to insulate.These connections look kind of bad in this blown-up image, but they actually look pretty neat IRL.The third image represents the bulk of the parts that you'll need to order directly from Lincoln Electric (through a distributor such as weldingsupply.com). The thumb-screw is not shown in the image; you'll see it installed in the second image. I did not order the middle bolt used to connect the electrical cable to the conductor block, as I had one that would fit. It is a 1/4-20 x .375 bolt, with washer and lock washer.Cut off everything from the mounting bracket except for the cube that the conductor block slides into. Then use a few foam/rubber washers [Harbor Freight - Item 67667] to isolate the metal of the block from the metal of the side wall. I used a hard rubber washer, the type used to seal a garden hose, as well as some of the larger foam washers. For added protection, I used electrical tape to cover the "edge" of the hole I cut into the sidewall of the toolbox, just to make sure there would be no contact. With DC, if the conductor block were to make contact with the metal of the toolbox it wouldn't hurt anything, I was just being extra cautious.I then bolted through from the outside into the plastic mounting "cube" with the exposed part of the conductor block facing the front of the tool box. You'll see a detail of this in the fourth image.