If it can be spot welded, it can also be bolted. My battery tray was eaten away when I bought the car so I welded my own out of flat stainless. I welded short sides so they would trap the battery and made a hold-down biscuit to grab and hold the bottom of the battery down.
It sure works better than that plank of wood the PO had in there. When I pulled the wood out I could see through to the driveway. - Dave