Erin Colleen Williams has crafted a steampunk replacement heart and liver. You can see it in action (worn) either on her website or on Brass Goggles, where we found these links originally. There's also a humor regulation set, which is to say the four humors of ancient medical theory and not something that's supposed to keep you from laughing (like American sitcoms).
That aside, as another idea for steampunk things...I think someone needs to write a country parody song called "Your Steampunk Heart." I would give that someone a dollar.