I don't know the correct term for this part of the rear springs. It is the plate right at the bottom of the leafs with 4 bolts in it that holds the springs to the axle, also where the rear shocks attach. Did these originally come from the factory on '69 Z/28's about the same width as the leaf springs, maybe a little wider? That is all I have ever seen. My '69 Z/28 has these with an extra length facing toward the rear end with 2 holes in the extra length. I tried to show what mine look like in the photos. I have never seen these before on any other '69 Camaro. Does anyone have any idea what this extra width and set of holes were for and if this type of spring holder did come as original on '69 Z/28's? Thank you.