Are you dealing with coil or leaf springs? When we set up race car suspensions we would usually mock things up with the frame leveled and tied down to a level floor with chains and screw-type jack stands, and either weak or no springs so we could move the suspension through its full travel with a floor jack. Once some measurements are made that way, it's usually pretty simple to fabricate sway bar mounts, 4-link pivot points, etc.
One rule of thumb on a dirt tracker is "Build it 3 times as strong as you think you need, and don't be too surprised if it breaks!"
Jerry
