I have a 2000 xj 9 inches of lift. And I have vibes coming from all four corners. :laugh:
But, on a serious note. I did have a head crack, but it wasn't until it overheated from a leaking radiator. And the vibes from the front shaft only became noticable when the slip joint went bad... which may have gone bad due to unnoticable vibes. who's knows.
A close friend of mine has 2-2000 xj that are daily drivers and both with about 130,000 miles on the clock and both have remained very reliable.
Personally, I'd hold out for a 99, though.