The key with this race is to take it in parts... at least it was for me. When I got to this race, the only vehicle that I was comfortable with that was qualified for the race was the Psychotic Fox, which nowhere near cut it on Legendary. Thus, I used the Psychotic Fox to beat the race on Recruit, which unlocks the One-Eyed Jack Maverick. After pursuing and hitting One-Eyed Jack, I then used that vehicle and blew away the opponents.
The issue in this race is all the debris in your path, and as it turns out, that will help you if you are good at dodging it. Most of the AI opponents will drive straight into the stuff all over the place, even on Legendary. Thus, while a bit nerve-racking, so long as you can dodge the detritus you will be doing alright for yourself. When you see the power line falling about halfway through the race (it gets hit by lightning), drive to the right side of the road, near the base of the power line. That will be the path to get through. This is not really one of the more difficult races, especially when you use the right vehicle for it.