Lurch O'Neil, from Wikipedia;
"A tall and strongly framed man, O'Neill was able to develop consistently as he built up his weight from 88 kilograms or 13 stone 12 pounds in 1965 to 104 kilograms or 16 stone 5 pounds by 1970"
When he was at Manly in the early 70s he may have been a bit bigger but he was a real giant back then, I can't think of any bigger players
(apart from one or two weighty Pommies who came out to play with sides like North Sydney)
(lol)