You need these plus a hold down bolt to drive your speedo Just the 'C' retainer. That looks to be a TH350 governor cap as it is on driver's side of case.and not a TH400. A TH400 has 4 x hold down bolts and is on passenger side of case TH350 TH400
Check what you got, this is 700R (4 speed - Overdrive) as 350 and 400 are 3 speed. If it is a 700R you may need different rear gears and to set you TV cable correctly or you won't have a transmission for very long.
note that the OP posted a picture of a TH350, the tail is shorter than a 700, although it looks very similar. I hope you didn't pay TH400 money for that transmission