If you need to get 12V auxiliary power from the the tow vehicle into the trailer, there is more than one way to it, however, if you have a 7‑way connector already on the vehicle, converting the trailer to 7‑way is probably the best way to go. This is what I did.

The project was actually pretty easy once I understood the three color codes involved. This is where some people run into problems. The instructions provided with my junction box/plug harness show clearly the two 7‑way color codes: RV 7‑way, and Utility 7‑way. The harness I bought was color coded to RV 7‑way, which doesn’t match up to standard 4‑way other than the white ground wire. The junction box is secured to one of the trailer tongue members with stainless steel square U‑bolts. The plug harness is secured with zip-ties but I need to change these out to screwed in cable ties for a more professional appearance. Fortunately, Runaway used standard color coding for the 4‑way trailer harness, so everything hooked up smoothly. 

The junction box/plug harness was purchased from Online LED Store, though Amazon. I highly recommend this product.