anyone know an easy way of caluculating the amount of lift achieved from various lengths of springs. Basically I need longer leafs for my '83 but want to keep the same ride height.The springs I have are too short due to the add a leaf the prev owner put in & shackle angles suck.I would guess a 2-3" lift is where Im at now. Is there anything that swaps in for this kind of lift? what kind of chevy springs fit?