I am looking to replace the factory front speakers in my 2003 Chevy Silverado. I know the factory size is a 6 3/4" size. Can I use a 6 1/2", or will I need a adapter mounting plate to get them to work. Also this truck came with the premium system, not Bose, So I have tweeters in the door also. Are mounting plates needed to install them also? Or do they drop in?