Lowered rear shocks question.
 

I've got an 03 Sierra 2wd ext cab that the PO leveled by lowering the rear end. I'm pretty sure that they did it by taking a leaf out of the springs. Currently it bounces something awful over road bumps and bridges.

Would a new set of shocks help the ride any? If so, what length shock should I use? I'm figuring a stock shock wouldn't work right since it's been lowered. Also at 206k, I'm figuring it could use some shocks anyway.

Thanks for any advice.