I believe your assumption is correct. However, just plugging in the proper harness may or may not enable all the functions. You would need to determine if the proper fuses and relays are in place. Later model Ford truck have the same wiring harness and they just leave out the fuses & relays for trucks without the towing package. In any case, having the wires already run should make wiring up a 7-pin connector much easirer. You might want to check out the website Trailer hitch, hitches and bike rack (800)298-8924 to see what some of the connector and harness kits look like to do exactly that on GM, Ford, & Dodge trucks. They also make generic kits to allow you to splice directly to thos 2 wiring harnesses you have discovered. Also, you could phone the etrailer folks or go to your local Toyota dealer and purchase exactly what you need. I discovered that the Ford dealer sells replacement 7-pin harness asemblies for less than the aftermarket a short while ago. Lastly, there is always the junkyard (excuuuusssseee me - in Steve Martin voice, automotive recycling center) to see if you can find the parts you want.