Motorcycle Questions? Ask a Mechanic.
There are quite a few options. The ring gear tooth count will be based on the starter you use. I recommend an '86-'15 Sportster or '07-'15 Big Twin. Those two starter types are self contained, meaning they don't need a separate starter jackshaft, drive gear, or support bearing.
You can find the starters beginning on page 874 (click the page number to be taken to the Drag Specialties catalog). You'll choose the ring gear to match the year and model starter you want. All the ring gears on page 879 are less than 8" in diameter and all bolt into place.
I hope this helps. Please let me know if I can be of further assistance. Thanks, P.J.