I don't think 3M makes a kit for the 308. You can buy a roll and put it on yourself or hire a professional installer to do a custom job for you. - good luck
Ive done lots of research on this. There was a 3M kit for the 308 - I have a PDF of it somewhere. It's no longer made. Another company also made a 308 kit - though far fewer pieces. A professional installer will use a roll & cut to fit. Ive seen it done on 308s and they do remarkable jobs & guarentee their work. And it's not silly expensive (though not as cheap, or satisfying, or mistake prone as a do-it-yourself)