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.)
The heaviest gorilla in captivity was a male of the mountain race names 'N' gagi, who died in San Diego Zoo, California, USA on 12 January 1944 at the age of 18. He weighed 310 kg 638 lb at his heaviest 1943. He was 1.72 m 5ft 7> in tall and boasted a record chest measurement of 198 cm 78 in.
UK Britain's largest captive gorilla is probably 'Djoum' of Howletts Zoo, Kent, whose weight is stable at 213 kg 470 lb. Another male example of the western lowland gorilla named 'Bukhama' at Dudley Zoo, W Mids was reportedly 227 kg 500 lb in 1969.
Source
Then there's also the fabled Gargantua, a circus gorilla with a claim to fame. He was called the largest and fiercest gorilla ever to be brought into human civilization, although this was probably just advertising hype. There are no trustworthy records of how big Gargantua actually was.
But if you want to talk really big primates, you should take a look at mister Gigantopithecus. At 3 m (10 ft) tall and weighing 300 to 550 kg (700 to 1,200 lb) was something you wouldn't have called a monkey to its face!
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.
that Gigantopithecus is one big bad
ape 
