Start with the solid subframe bushings first! They are the foundation of the entire IRS! Actually, if you can swing it financially, do everything all at once! You'll have to lower the cradle to do the driver's side toe link so might as well do it when you have the cradle down for the bushings! Also, when you do the trailing arms make sure you replace the outer bushings if the don't come with the arms.
Not a Camaro but it works for now!