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There are 2 species - the Western and Eastern gorillas, and both species have silverback males. The larger of the two is the Eastern Gorilla. The maximum size of a male gorilla can be over 225 kg (500 lb) and 1.83 m (6 ft) in the wild, with much heavier weights recorded in captivity. (Although I can't find a decent reference to the recorded sizes either.)
All that said, I can't find a reference to the biggest wild gorilla captured either, but if they say the maximum size of a male gorilla can be over 225 kg (500 lb) and 1.83 m (6 ft) in the wild, then that'll probably be your record.