how to remove spring clips on 94 suburban rear leaf springs to install new plastic insulators?

Trying to cure the rear spring slapping noise when I go over bumps. Bought 8 rectangular pads (the old ones were paper-thin and mostly
destroyed) and 4 roughly H-shaped insulators (or are they called inserts?; Flagg Suspension Parts #GM9); the 4 remaining round insulators on the truck are still good. I was able to install the 8 rectangular insulators between their leaves when the truck's on a lift with springs hanging (by spreading the appropriate springs apart with a chisel), but the 4 H-shaped plastic insulators underneath the steel spring clips that keep the stack of leaves from separating too far when bouncing are a different story. The steel clips that are in the way seem to be pressed into a round hole in the spring from the bottom; I couldn't budge them out so I could slide the clips forward or back and install the new plastic. I've tried hammering and also a pair of C-Clamps with a small spacer to try to push out the clip from the spring. My C-clamps didn't have a fine enough thread to deliver the oomph probably needed. I hesitate to heat the spring with a big torch. Do I have to take the spring stack out of the truck, disassemble the whole stack and use a press? At that point maybe I should just buy new springs if I'm going that far. 285K miles on the truck.
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