There is an obvious, everyone lives happily ever after, ending to this story but I don't know how realistic that would be. You've set the individual feelings these people have for each other pretty strongly to be able for them to make any of the necessary 'switches' seem really plausible.
Of course, you have the option of letting your characters end up miserable ever after.
Rachel and Clark have already broken up, and we all know that Chad and Lois will break up (See the title), but I'm curious to see how well you sell the final outcome and where it will leave these four people.
Your writing has been excellant so far, so I have confidence that you know where you're going with this.
Consider me just another gentle reader along for the ride.
Tank (who is not a big fan of Chad and wouldn't care if he didn't survive the ending of ths story)