FYI: Be careful, I read an article a few years ago and, if I remember correctly, the '00-01 have a reputation for cracked heads (yeah, I know... I just bought a 2k XJ). I think they opened up the water jacket channels near the #1 and #6 cylinders. I think there is also some minor bracket changes too. Of course, I assume you've also posted on one of the XJ forums.
Good luck...