I feel every bump when I drive what am I missing?

Tire inflation, wrong tires, wrong parts used in the rebuild.

If you like a smooth ride, don't buy a muscle car. It's likely that that's the way the Challenger was intended to ride. If you start with a rough riding car and want to smooth out the suspension, there's not much you can do. Softer springs won't do much except drain your wallet. There are softer riding tires, but not by much. Live with it and enjoy it as I used to do. Or sell the car and get a minivan.

Give it a week . New shocks can sometimes ride stiff