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

Demon
I have gone down the same road, and the offset was an issue with a stock length rear axle. I am running 315ZR17 on the 17"x10.5" bullits with everything set my ground clearance is 4.5" at the frame rails. However the coil-overs are at the lowest hole on the lower supports I can always raise the car twice by 1.5" increments.
I would love to run the 335 KDWs but I don't know if they will mount on the 18x10s. According to BF Goodrich the rim width range is 11.5"-12.5"
The Bullit rims 18"offset is actually .7" greater than the 17" that I have.
the pic is at ride height, your look should be close.
Andrew