All of us in at the time believed that organ transplants were forbidden. There may not be a quote that states a d/f penalty but it was well understood. You are in no doubt with comments like this
Wt 1967 p 702/704
“. Those who submit to such operations are thus living off the flesh of another human. That is cannibalistic. However, in allowing man to eat animal flesh Jehovah God did not grant permission for humans to try to perpetuate their lives by cannibalistically taking into their bodies human flesh, whether chewed or in the form of whole organs or body parts taken from others.”
The full article, a QFR, is worth reading on Watchtower on line, if you have an interest.