Pre-Zaire Foreman...hmm, at this point I have to give it to Usyk. But it would be a very tough fight. I think both prime Foreman and Tyson lose tough decisions, both are getting beaten around the ring to some degree toward the very end. The fight would be close the first six rounds. Obvious UD for Usyk in 12, though he has some extremely scary moments. Perhaps strangely, I see Liston outpointing Usyk, go figure.
No sane person should be picking any version of Foreman in this fight. Usyk is even bigger than any pre-80s Foreman.