Best thing to do is take your old one to the parts store or dealer and get one that matches. Otherwise you could be down for a long time.

I'm thinking it's either Delco or Mopar. XJs used a lot of GM parts.

Yes, that is another good option.

Just checked, of course I ordered the wrong one. My distributor ends in 28. Ordering the right one from Rock Auto is still half price of the low priced ones at O’reilly.