Probably been done before, but if it weren't for redunance and repetitiveness, we'd run out of things to talk about. In 1992, a 40+ Larry Holmes outboxed Ray Mercer in one-sided fashion then went the distance with the reigning Holyfield. So what does that version do against today's top heavyweights? My thinking is that he isn't beating Wlad or Vitali, but has a hell of a chance against everyone else.
Then again, Fast Eddie Chambers might have outslicked him to a close decision the way that Spinks did in 1985, but who knows.
The Klitschkos are bad matchups for him. Other than them though he may be the best. Chambers-Holmes would be close and I'd see Holmes being able to beat Povetkin. There's few fighters in history that could knock out even 92 Holmes, and Haye probably isn't one of them. Holmes jab would likely enable him to win a decision there but Haye's reflexes and countering would make it a tough fight.
He would be rank number 3, the Kilt brothers would be over him, prime for prime is other matter, but this is 40 plus Holmes we talking about.