Somebody was making a 3.0ish gearset for it several years ago. Wagoner Machine, I think. I don't remember what it cost, but it was a big chunk of money. You also had to ship the case to them to be modified so the gears would fit. I think the planetary-based reduction boxes beat it on price.
So short answer, you might find one used. I know a guy that bought one new, and IIRC his sale price was reasonable. But it's probably not worth modifying one on your own dime.