Speedometer

37 tooth is in the ballpark for a 25.5" tire. It's going to read a few mph slow with the 37, a 36 tooth would be the most accurate (according to the chart in the Year One catalog).
The "32-38" numbers on the gear housing go at roughy the 6:00 position when you install it. The clamp will align it to the exact position where the gears mesh properly.