OA Naga were not updated in 3.5.
Only the Shinomen Naga were, which would only apply to DMs accepting Dragon magazine.
The Naga described in the Campaign Setting were specifically mechanically distinct from the Shinomen Naga in order to allow the former to be a more accessible PC race. This was explicitly stated.* And while their stats were lower, their LAs were also lower (though ridiculously excessive, save for the Greensnake) and they were all Large. (Note that Shinomen Naga Greensnakes were not Large, but Naga Greensnakes of the OA Campaign Setting were, like all other Naga, Large -- with 40 ft. movespeed).
*The update of the Shinomen Naga has no bearing on the existence of the Campaign Setting Naga for this reason. The Shinomen Naga were listed as monsters and updated as monsters. The CA Naga were a PC race and were mechanically distinct. (Indeed, their powers and stats don't match up between them, making the entire concept incoherent. Shoddy doesn't begin to describe the design incompetence.)
So there is, in fact, one 3.5 Large 0 LA race in existence, fully legal, not updated from 3.0.