Springs are generally linear when force is considered. In other words, for every inch of compression you multiply it times the spring compression factor to determine the force exerted. If both springs have the same compression factor the taller spring would be exerting more force if the spring holders are the same distance apart. Logic would state the taller spring would be on the driver's side to accomodate the added weight when driving alone. If the springs have different compression factors it becomes more involved. I would be interested in what an automotive design engineer would have to say on this subject. In the mean time, put the original springs back in. The 71 springs probably have much higher compression factors and your alignment and tire wear will suffer.