Dunn, Milton, Claussen (or Ramierez) and Majewski (we pay Milton's final year) for Billingsley, Broxton, Repko (or Loney), Antonio Perez and one other prospect (did the Dodgers deal Navarro?). The Dodgers won't do it, but I would.
[EDIT] Penny has talent, but he's been spotty and injury-prone. I know that the Dodgers aren't gonna part with Billingsley, but Billingsley AND Broxton is the kind of return I'm gonna demand to deal the Donk. It would have to knock my socks off. Penny doesn't do it.