Last season was the first these guys played in the Manning offense youngers guys like Franklin/Beadles and even Walton before he got injured all improved dramatically.
The biggest thing for the OL is continuity of playing together in the same system. I don't think there a pressing need to change our starters, just let them continue to develop and log snaps together.
We have sufficient depth at G/C as well with Blake, Koppen (should be resigned) and Ramirez who started playing really well at the end of the season.
Maybe we could draft a T prospect to compete against Clark but I don't see a real big need here.