...so what would be involved if it were the other way around? I see many good deals on presses in the used market, but we only have single-phase power in this area.
In the case of this particular M&R press I believe it would be the same, just swap breakers/capacitors on the panel, possibly change a setting in the panel.
My guess is that it would work on any machine that is built and sold in both 1ph and 3ph. This presumes the press would be made with identical components save for a handful of electrical parts at the panel. But like I said, if you are large company manufacturing a machine, you probably don't want to stock a complete alternate set of motors for the 3ph models v. the 1ph. It might save a bigger operation a lot of cash trapped in inventory to have universal motors/parts so my guess is that most companies have this practice. Just a guess though, always ask!
