Was is the "Rivera starter jackshaft kit"?
The starter jackshaft kit is their part# 1185-0004 and the 10-84 ring gear set is 2171-0011.
www.riveraengineering.com page 223
I replaced the jackshaft (kit) as I didn't want any more starter problems (didn't know if mine was bent or worn). The jackshaft goes between the starter and the starter bendix (pinion gear).. You have to remove the inner primary to replace the jackshaft and related parts. You do not have to pull the inner primary to replace just the starter pinion gear.
You can read the install instructions on Rivera's website. When you install the new ringear, the bevel goes AWAY from the pinion gear. Rivera's website says to put bevel towards the pinion gear but that only pertains to belt drives for clearance. I called them and confirmed this. If you read Compufire's instructions, their's says AWAY from pinion gear (bevel edge).
You probably already know that but just in case. Bob