You should be able to still run duals. My exhaust shoots out right in front of the dually fender, but I have seen guys run duals through their bridge in the back.
Do some searches on layitlow.com and streetsource.com
I would think you should be able to run 3" duals. now if you had a big diesel and were going to try to run dual 5" pipes, that would be a different story. HAHAHA