How do you determine "ride height" to make suspension mods??

I already checked and American TT M's don't come in 18x12 either -- So regardless I am stuck with either widening the Bullit wheels or the American TT M's to get them to the 18x12 that I need. Since I have to widen them I can have the wheel shop set the back spacing at what ever I want. I am also waiting to hear back from COY's on a custom set of C-5's --- Figure by the time I buy rims, have them widened, then have the refinished to look right, I am going to have some coin in the rims so I am just trying to work out the most cost effective way of doing them.

I hear ya. I'm trying to nail the boss down on a price. The deal with going to a 12" wide rim is that nobody makes a hoop that wide. You have to take two hoops cut them apart and make a 12" wide hoop. I've been on him, but he gets sidetracked easily.