25mm or 35mm are too much. Your wheels will actually stick out past the fenders a little. They don't work with factory wheels because of the casting on the back of the wheel casting in relation to the mating surface of the hub. Where the spacer mounts to the factory lugs the lugs are to long and will contact your factory rims. Blue oval industries sells a wheel spacer kit for the 99-04 that will work and it comes with extended length lugs to use. But I recommend purchasing the arp ones that AM sells. This is what I have and it works great. Good luck.
Best 1/4: 1.90 60ft. - 12.15 @ 119mph on Street Tires.
460.25rwhp & 408.28rwtq SAE on a Dynojet 224xLC
Tuned by Matt Lepkowski, owner and operator a Performance Evolution in Smyrna, DE.