i have a 68 coupe with a 289. I have maier racing front coils and billstein shocks. Would the maier racing rear leafs be a big upgrade over grab a trac leafs? Also, should i go with billsteins all around or are there more cost effective rear shocks that would perform similarly. I dont forsee much track time or road racing with the car. I just want a good performing street vehicle. Any help would be greatly appreciated. Thanks a lot