You need the adapter in order to make the turn signals work. You cannot wire a 4 wire harness directly into the Ranger. You need to wire in the 5 wire plug and then use an adapter or else you need to find the plug-in for the Ranger wiring harness.
you can tap the brown wire into one of the tag light wires..that will give you runing lights. You then need a test light to find out what is the wire for the left/right turn..i usually just take a tester or light bulb (rigged to llight up) and then a safety pin..with the ground on a ground..take the tail lamp off..with the safety pin..poke the wire to make contact..then connect the other wire from the tester or bulb to it..see if it lights when you press on the brake. If i remember yellow is left turn on trailer and green is right turn. It can be done..but remember when you do get it to work...you will need a new TURN SIGNAL FUSE ..it will be marked for trailer towing..if not your signals will blink really fast...and the factory fuse will burn out.
I just stopped by the Mart on the way home and picked up one of the adapters. ~$25. Kinda pricey, but I'll say that it took me 10 minutes to install and tuck cables out of the way and it works perfectly. Snap, snap and a few zip ties and it is done.
I'm pulling a 14' tandem axle flatbed next weekend. No worries about the wiring now.