Even though my 99 xj8 has only 29 k I wanted to go ahead and change out the plastic for metal versions. Based on my year and s/n 854xxx I thought I was dealing with a A27 engine. Ordered parts and met w mechanic to begin. Taking off left cover first, I find I have a nice thick orange gasket. Also have the 3 ring seals of the A26. The replacements I had were thin black and feeble looking gaskets. Mechanic said he would rather clean up my old cam cover gasket than use what I brought him.
I decided I'd rather make the trip to a dealer and match what I have than to use my old one. Just pointing out as others have that you can't trust that you will have an A27 because of car's date of manufacture or S/n.
Hope this helps someone else to look before you leap.

 

You can tell by the cam covers what year u have. They are different.

 

Does the VVT solenoid valves come out the top of the valve covers? If so it is an AJ27. If they are on the front of the engine it is an AJ26. The AJ26 gasket can be used on the AJ 27 with some modification. Perhaps someone had the covers off before(?).

. . . and welcome to the forum!