My 64 futura hardtop has what I believe to be original 3 leaf rear springs. Worn out, as well as the bushings. Before I replace them I need some advice from anyone who has installed / rebuilt the rear suspension. I do not want to disturb the ride height. The car is level front to back. The shocks are new but I notice a slight sag on the left hand side. Also the car is not as stiff as I would like. Sortta spongy. The whole front suspension has been replaced. Please advise. Any vendors you would recommend will be appreciated. The only 3 leaf springs I can find are from MACs. I'm a little nervous and confused about going with 4 or 5 leaves since the car has 3 leaves on it now. Thanks!