Sanity check

Ok, an update. To avoid having to use an adapter, then needing a different pushrod, I went ahead and bought a MC for a 73-76 dart. The one with the 15/16 bore was/is for power brakes, and the other one listed for manual brakes had the larger bore (seems backwards to me but I looked at a few different suppliers to make sure). Now, though, I have a master cylinder that doesn't have the retaining groove inside the pushrod grommet.

https://www.oreillyauto.com/detail/...101571/4559072/1975/dodge/dart?q=101571&pos=0

Pretty sure it's not going to work, and if not, which one do I need to get.