Tomreid

I've got a '94 Z28 with a LS1 swap. It's a dedicate track (car road courses), and it's in need of alignment. I want more negative camber upfront then the stock lower control arms allow. The old bushings are shot as well. I'm looking at upgrading to adjustable control arms. My mechanic wants me to replace both upper and lower control arms. I thought all I needed was lower arms. The price difference is significant. Do I only need lower arms or do I need to replace both?
Thanks