I've added an additional leaf spring pad on the drivers side on top of the axle to try to push the wheel further downward away from the body. I know it's not life or death, but it just bugs the hell out of me.
Any shim between the spring perch on the axle and the top of the spring lowers the body. New springs or OE? If OE, then they may need replacement. If new springs, then they may need to settle out over time, or they are from two different batches made.
Try to find and get a four-corner weight check. This will tell you the heavy corner. Obviously, the load within the car is distributed evenly?
Check distance between the front subframe and floorboard at about the front seat area underneath. Your hand should slide in up to your knuckles, no further. If your hand goes through, then front subframe is bent or the mounting pads on the body are pulled out, or damaged.
You might also check the condition of the body bushings to see if they need replacement.
Jack up the rear axle at the hogshead and check the height of the front fenders, they should be relatively even. If the driver side is down, then I would suspect a front spring change.
You started to do a fix, but I think you could get better results by taking your extra spring and insert the thick end, if the leaf is tapered, between the spring perch and spring on top of the OE spring on the rear section of the OE spring (between the axle and shackle), you would be replacing the top pad with the new leaf. The front edge of the new leaf should be even with the front edge of the perch. Now clamp it together with the shock plate.
Make a clamp from two 1/4 inch thick steel plates, 2 inches wide by 5-6 inches long. Drill a 17/32 inch hole in each end of each plate just outside the width of the OE spring. Place a plate on top of the new leaf and on the bottom of the OE spring and clamp with Gr 8 1/2 inch bolts and Locknuts with flat washers.
Now slide the newly made clamp up the spring to clamp the new leaf together with the OE spring, towards the shackle, until height is acquired. Finish tightening the bolts. You're done.