I don't think you'll find anybody willing to donate a lung from their body. LOL what a visual...
Anyways, an Australian would probably work, but impractical as they are almost impossible to get (Thanks to Neo hoarding!) The next pick would be a South American, BUT care must be taken that 1) the lung gets enough food, and 2) that it doesn't get bitten on, and 3) that the lung does not like to bite tankmates.
Number 3 is common.