I replaced my X's shocks and am giving my old ones to a friend at work who has a quad cab Frontier - both 01s. The shocks only have 15-20K on them, and hers are original.

Will they fit?

I thought the Quad Cab fronties and X's used the same chassis/etc...

You are correct. The 1st gen frontys and xterras have almost identical chassis BUT if I'm not mistaken, I believe the fronts have a spring-over axle in the rear compared to the spring-under of the xterra. I would pull one of her rear shocks off and fully extend and compress it and compare the lengths just to be absolutely certain.

That is, if nobody else corrects me and they actually are the same. Another option is to call AC and ask them. Volrick and those guys can tell you for sure.

should be no problem at all, I am running a sl and shocks off of a fronty right now.