Securing speakers

[Rambo2]

Hello,

I am fairly new to the site, so I hope I am doing this right. I have a 1970 GMC and am ready to start putting the stereo in (no dash cutting). I have the head unit ready to mount in the glovebox, 2 4" speaker pods in the back corners of the cab and the 2 6.5" kick panel speakers. I am wanting to replace the generic speakers that came with the kick panels with Kickers I have. The dimensions are all good, but the holes don't line up on the speaker and the enclosure for easy mounting. The plastic enclosure is very thing, and I fear it may crack if I try and drill new holes in it. Is it possible to seal the speaker to the enclosure with an adhesive? I don't want to comprise the sound or the structure so any car audio advice would be appreciated.