Speaker Mounting
#1
#2
I've fit 6x9s into 5x7 holes on various vehicles without cutting anything. Sometimes it dropped right in, sometimes it would rest on the lip of the hole then pop in once I started screwing it in. Pretty sure I used self tapping screws 99% of the time too. But yeah, may need to grind the inside of the hole a little. May depend on speaker brand? IIRC some people did have to do a little grinding or cutting on their trucks but worth a try to just see how it goes without doing either.
#3