I would recommend changing the control arms since it will reduce weight(not like you need that spring perch anyway). Furthermore, I can not believe someone did not mention this by now, but you need to find some way to brace the rear shock towers. They were never really designed to support the weight of the car which is why you can have the shock towers tear loose along the seams in stock form. Do not buy a tokico shock either since the lower mount is not strong enough to support a coilover.
sorry, i am just doing front coil overs. i am leaving the rear alone. i already have bbk upper and lower control arms on the rear and i happy with them.