Holes in the end of those leaves? Not to hold things together, but for the waxy fiber pads to serve as "anti-squeak" devices. The "HD" spring do not have them, it seems.
The main leaves are held in place by the end bushings and holders. The complete spring assy is held together by a center bolt, which is hidden by the attachment to the rear axle. Then secured to the axle housing by the U-bolts.
It is not uncommon for some drag racers to remove the rear clamps so the spring will separate on a hard launch, which will change the pinion angle a bit, with the end result of "more bite" on launch from the starting line. I have seen some "separations on launch" that would surprise you! YET the cars operate as normal in regular driving situations.
I was trying to figure out how the shocks were close enough to the brake lines to rub on them . . .