Depends where your pockets are.. Some are confident in the mark VIII fans and claims are that they flow better than almost all aftermarket fans....which you can pick up at a junk yard for around $40. But they need a proper controller to run them. Most are using dc controllers I believe because that fan has such a high current draw. There are lots of topics on them. That is my plan, mark VIII fan and DC controller when I get the time. Most will tell you that is your best upgrade, fuel mileage, throttle response and a hp gain you can feel. BTW, I have the same truck.. 99 5.4L w/ 3:73's running 33x12.5x17's and seeing around 14-15mpg right now. Hoping for 16 with the E fans. I have been running the gotts mod on both this and my last truck, good improvement for the $6 it costs to put it together.
Last edited by Toyz; 10-27-2011 at 01:36 AM.