50 feet - probably not. Scaling from a 6 foot, 400 lb gorilla by the square cube law, the 50 foot gorilla will be 8.33 times taller and thus:
$8.33^3 = 578$ times heavier
$578*400 = 231204$ lb or ~116 tons
That is at or beyond the largest sauropod dinosaurs - a recent estimate published in PLOS One (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3864407/) suggests 83 metric tons (= about 91 US tons) for Argentinosaurus, which is often considered the largest (in terms of mass) dinosaur. (The introduction to that paper also has some very relevant general information and cites about biomechanics at very large sizes.)
However... the sauropod dinosaurs had pillar-like legs, unlike Kong, and also had a suite of helpful adaptations no mammal has (heavily pneumatized and thus lightened skeleton, egg-laying and reproductive maturity far below maximum size which avoids the problem of very low reproductive rates faced by huge mammals, non-chewing-intensive feeding style).
But the smaller end of Kong portrayals - say ~20 feet and ~7 tons - is well in the mammal range.
And while elephants have pillar-like legs, Tyrannosaurus was a biped with much more 'athletic' leg type in the ~8 ton size range.
With the right evolutionary pressures, I'd expect apes to at least be able to reach the 2-3 ton range many mammal groups have broken into, including some very improbable ones (glyptodonts - basically giant armadillos - were >2 tons at max, and Megatherium, a sloth, was 4-5 tons!). The therizinosaurs were also 'grasping' browsers in this kind of size range, up to 5 tons.