There may be a post regarding this, if so please point me in that direction.

So a friend of mine just picked up a 2k xj, and after buying it asked if Id come take a look at it. So I checked it put and besides a couple simple things he had sludgy radiator fluid. So after some research the likely hood of a blown gasket was soon realized. My worry is that it seems Xjs built around that time are known for cracked heads.

My question is what heads are interchangeable? Would a pre 2k or pre 97 head cleanly swap his?

 

You are right about that year with the crappy 0331 head cracking, But before ripping the head off verify that there is water in the oil also you should do a compression test on her too. With a little luck the PO just neglected the cooling system and it need a major system flush.

 

I had sludgy looking coolant in my 2000 XJ also. I flushed it out and installed a new thermostat and water pump. It's fine now.

 

I did recommend to him that he does an oil change and radiator flush. I will do a comp test I have the kit, any idea what the appropriate reading should be?