New here have a fe questions.

Ok I have had my 89 xj for about 5 months or so.
I havn't any problems with it untill I got here suck in a mud hole.Well I fixed all that I screwed up on it.
Im not sure if my motor has had a rebuild or if it the orignal one.Where can I look on the motor to see if its the original one.The reson I am asking this is because the odometer is saying well about 243,000 give a take a few.Now the other question I am thinking of updating the motor to a newer one how new can I go. What years will work in my 89 XJ oh it is a 5 speed as well.

Get a compression check and that will tell you how its doing. 253k miles is pretty common on these things.
KH

Unless you're willing to do a lot of electrical rewiring, including new speedometer, and a whole lot of other stuff, you're locked into the 87-90 Renix injection system. Unless your 89 is very special in other ways, it probably doesn't pay to try updating it, especially since the Renix system works very well anyway.

As far as rebuilds are concerned, it could mean that the engine was rebuilt and put back in, or that a rebuilt engine was bought and dropped in. If the latter, you'll usually find some kind of ID plate glued on the side of the block. If the former, you may never be able to tell unless there is some internal part labeling you can check, or service records. As Kevin suggests, check the compression, and if it's good and the engine runs well, count your blessings. At 243 thousand miles, it could be rebuilt, or it could be original, and either way it could keep going a long time yet if you take care of it.

My '88 is currently at 244,450 miles and still delivers 21 to 23 MPG in highway driving. An odometer reading of 243,000 on an XJ is no reason to even begin to suspect a rebuilt engine.