This game needs to be Terrell Lewis' breakout game. He will be going against a backup LT which he should beat consistently. If Lewis can have an impactful game, the Rams win.
Alternately, the Rams need to stop the Niner's run game. I would play both Gaines and Robinson inside, keep Floyd where he is and play Donald against a backup OT. Then with Wagner and Jones behind them they should be able to stop the run and put pressure on Jimmy G when he passes.
The key will be for the Rams to play a clean game and stuff the Niners run game. Force Jimmy to pass to beat them and I don't think he can do it.
BTW I think Jimmy will end up in Seattle next year.