cutlassclay

So I recently got a new (to me) th350, after I installed it I realized I had no speedometer. the driven gear was present, so I pulled off the tail shaft housing and found no drive gear. So I'm basically going to start over with the gears. I've tried to do calculations but numbers are not adding up right. I've got a 27.83 tall tire and 3.73 gears, can anyone shed some light?

Also when I pulled off the housing i found a yolk seal cup thingy. Any idea how to get this off because the speedo gear goes behind this.?.

Thanks clay