back in the late 90's when i did this, i just held the sign up to the bottom of the frame with my floor jack, and traced it out with a sharpie, i think i had to take the front wheels off, i did drill a hole for changin oil, and i used 4
u-bolts to hold it on, it lasted for years, till one very big downhill jump, in the strip mines, bottomed out, caught a big rock, and ripped the front loose, bending the sign, took the back bolts loose and pitched in down the hill, im gonna have to go back up there when my motor comes back, and see if it's still layin around