Not needed for wood
A speed reduction "kit" for metal cutting would have to reduce the 3000 or so FPM down to 300 FPM at the most. That means a 10:1 ratio, usually not practical for a gear reduction and it would be expensive. A jack shaft and large and small pulleys works just as well. BTDT myself. That was long ago before I bought a dedicated metal cutting bandsaw. Aluminum cuts OK at wood cutting speeds depending on thickness.
I have a Milton dual speed bandsaw, but uses a drive disconnect with 2 different belts you have to swap out. I have yet to try the high speed arrangement because I have other wood cutting bandsaws.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)