Tooth Count and Housings
Not sure if you got the answers your looking for yet. The drive gears on your Output shaft can be either 14 or 15 tooth counts. The plastic one is a 15 tooth gear, the metal one looks a lot smaller and could be incorrect. You will need to trace one tooth on the gear from beginning to end, then count the remaining teeth to determine the count. 400 driven gear housings will work with any drive gear, they range from 34-39 and 40-45. To determine what you need go to transmission center.org to use their speedometer gear calculator.