I use .308 Lapua brass in my 7mm-08. It is a simple matter to neck them down in any 7mm-08 FL sizer die. I turn the necks down slightly for uniformity but it isn't necessary to reduce them to fit in my factory chambered barrel. However, it is always prudent to check the loaded neck diameter when necking brass down.
The .308 brass is slightly shorter than 7mm-08 brass would ordinarily be but this does not present a problem. You will probably never have to trim the brass other than to initially uniform their length. (If that's even necessary)
While you could also use .243 Lapua brass, which is longer than the .308 brass, I believe there is a shoulder angle issue to deal with. You would probably need to fireform the .243 brass so I never bothered with it.