The 3.0 arms are different in order to use the 3.0 uprights. If you want to just use the shocks and towers they will work with your 2.0 fine. Like the guys said, best to stick with full 2.0 or 3.0.
I converted my 2.0 to a 3.0 piece by piece and have tried different configurations of 3.0 towers and shocks with 2.0 arms and uprights/spindles, full 3.0 geometry with 2.0 chassis, etc. IMO the 2.0 was better stock and 3.0 is better stock than any hybrid I tried. The last piece of the puzzle was the 3.0 chassis and layout. Once I got there I knew what all the raving was about. Just enjoy the 2.0 or sell it and get a 3.0. Either way they're both great cars.