The Stovebolt Site Forums The Shop Area Paint and Body Shop Battery Tray Removal/Install

I am attempting to replace the battery tray that is under the passenger footrest area because the bottom of it is rusting through. The original tray is held in by some sort of, well, I don't know the right terminology for it, honestly. Some sort of rivet-type of thing. The point is, it is not bolted in. I have sawed off the one set of "buttons" on the tray side and am left with what is shown in the photo attached.

I am looking for advice on how to proceed. I tried hammering them a bit, but they aren't budging. I don't really have experience or tools for metal fabrication, so this is new to me.

Thanks!