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The bushing is there to take the wear instead of the plate slot. I asume your talking about the pin and bushing on the bottom of the distributor shaft to limit mech advance.
If your wondering how your engine will run with additional mech advance ,it would,nt hurt to remove temporarily, but once you figure out what you want for total mech advance open up the slot the bushing rides in for permanent setting. The bean counters at GM don't let the engineers install extra parts just for the heck of it.
If it's installed it's for some purpose.
Bob