NWB300

I bought a proxses fuel pump assembly and when we went to put the assembly in the bucket it doesn't fit. What's happening is the edge that my finger is pointing to is cutting into the side of the bucket and if we press hard enough it will only go on about 80% of the way. It's almost like the assembly is slightly larger than the bucket and i'm only having the issue on that one side. You can see in the other pic where the edge is really tight against the bucket. We tried for hours to get this to fit thinking we were doing something wrong. Anybody else have this issue? I was thinking of just cutting that edge of the bucket so everything sits but i'm not sure if a hole with make the bucket useless and if I grind down that edge it will cause oxidation with the bare billet aluminum. I'm running E85 so I don't know if there is a paint or primer I could use if I went that route. Any suggestions?