If you pull the whole side panel you can get to the weld tabs. Think another on here burned or.drilled them, I’d check before you did either. Think it was a BO upgrade thread.
I didn't even attempt to replace the factory "sub" I removed it and hung mine on the tailgate I lose a bit of room but not a huge deal. IMO The OEM enclosure isnt really solid enough to handle anything more than what they put in it. Im running a 10" Kicker Comp-R with a 500.1 Kicker Key amp in a sealed enclosure and after autotuning with their software it sounds great.