Yep your right. Just bolt a plate to locate the upper control arm holes and the down bar is the wheel centerline.

You need to measure control arm angle on a stock vehicle or at the very least keep the lower control arm level or slightly up. Your other issues will be fabbing brackets for coil overs (I doubt you'll use the transverse spring) and probably lowering the rack for oil pan clearance without affecting geometry. You can make them or buy them. http://www.streetrodgarage.com/c4vettesuspension.aspx

Thanks, Craig