Golovkin wouldn't have to make 160, so he would be weighing like 175-180lbs and Fitzsimmons was 167 lbs when he KO'd Corbett, who wins this matchup?
The footage I have seen of Corbett suggests that Golovkin has nothing to worry about here. Hands down at his waist, arm punches, generally strange looking balance ... he may have been a pioneer, but in this instance its like pitching Alekhine vs Carlsen.
I think that Corbett was fast and tough enough to take a decision here. He'd be much bigger fighter than Golovkin and we have never seen GGG above MW.
I don't see, what Corbett can do here! Sure, some nifty footwork - but what else did he have, that could possibly trouble Golovkin? I think GGG stops him pretty early, to be honest.
GGG could come in with no sleep from a 2 day sesh on the packet, fight 2 bouncers, get a blowjob whilst warming up, and take smoke breaks between rounds, and still get him out of there in 6.
Corbett much too fast. What you see of Corbett on film, and I mean the higher quality footage against Fitzsimmons, the way he dances around the ring popping that jab, what will Golovkin get done? Remember he battered Fitzsimmons for much of their fight and over the distance Golovkin was used to fighting he would have won on points. Corbett is too quick of hand and foot and too durable for Golovkin and his slow punches. Bad style clash for Golovkin here.
I see a bigger, slower Proksa with less situational awareness. Golovkin has always been good at cutting the ring off on fighters, and I'd pitch his close defence and heavy jab against Corbett's arm punches all day.
Cutting the ring off against a bigger quicker man is much easier said than done. Golovkin isn't going to out jab him and there's no way he's getting past the jab himself. I honestly think he gets shut out here.
He's on YouTube against Fitzsimmons. There's two versions of the footage, one is a lot smoother by the Library of Congress. Important to consider though is that the film is the only film we have and its only a short clip. To get the full picture you have to read fight reports, descriptions of other performances, contemporary reviews. Ideally you'd buy the book by Pollack to get a full picture.
Corbett for my money is the most overrated classic fighter in boxing history. His wins over top opponents are very exaggerated and need context, and he also lost to the best he fought. His best win was a completely shot, obese, alcoholic Sullivan, who he couldn't actually KO for a great deal of time. He honestly wasn't all that as a technician either, as his legend states. He couldn't even outbox Sharkey in a 4 rounder. However, he has a good deal of size and strength on GGG, was a clever fighter, tough, good feinter, and was an absolute speed freak. I do find it hard to pick GGG over him due to that, especially if the rule set favours Corbett (you didn't specify - modern, classic, 1950s, glove size, rounds etc? Makes the difference in the outcome). Corbett is both the bigger and faster guy here. GGG is fundamentally better, but really loses out in speed of foot and reaction.