Ok, I can't figure out what would be the best way to split these, I'm leaning toward:

4 squads
10 marines, ac, fist, las/plas 225

But here's what I've got, chosen might be a good use too.

24 bolter marines
6 plasma marines
6 lascannon marines
6 ac's, pistol, fist

thanks for the advice, the rest of my army will be one or two lash sorcerors, dependin on the points and up to 9 obliterators.