his chestplate offers constant diagnostics as to the function of his pulmonary, adrenal, and nervous systems (those 3 main lights). Lucas has said that he's 3/4th's mechanical without specefying how that's distributed. his heart and lungs are obviously still there though i'm sure a majority of his other organs have been replaced due to concussive organ failure from his massive fall (he doesn't exactly fall IN to the molten rock). and aside from the other prosthetic stuff that i've mentioned a billion times on this forum, I'm pretty sure that his eardrums and some of his teeth have been replaced after a head injury like that. other than that, his entire head, most of his spine, and the organs within his rib cage should have been fine for the most part.