My Toyota came equipped with 3.73 gears. I don't know how hard it would be to cut down an axle to fit under your Tracker, but there's lots of Toys out there.
Here's a page that lists
Toyota axle codes so you know what ratio you're looking at.
Kubota's current 1803 engine is a 1.8l 3-cyl rated at 28hp at 2700rpm. The V2203 is a little older, a 2.2 4-cyl rated at about 48hp, but that's the NA version. I don't think it was available factory turbo, but