Well thats too bad. I don't know what that ear is, but it probably had a purpose.
Problem with these pumps is that they're around a 100k mile replacement item. Junkyard pumps are likely to be near the end of their lives, if not dead, especially if they've been sitting and rusting for a while. I went the used pump route when I did mine, ended up putting two pumps on it. The first pump was a good runner when pulled, and it didn't run worth anything when it got onto my truck... died at every clutch push, ran terrible, low power, smoke etc. The next pump was also a supposed runner I got from someone else and I couldn't even get it to pump fuel to the injectors. Once I spent the $440 its been running great since. On a van I would rather not go through the pain of doing an IP twice.
Its your RV and you're welcome to attack the problem any way you see fit, I'm just trying to save you some pain and time. It does look to be a cool old RV though, and when its running right it sounds real good. Hope you get it figured out,.