2001 LP Dana 30 shafts into an 88 HP 30??

I have a 2001 XJ sport with a LP Dana 30? Does this have the good 297 u joint shafts? How to tell?
I have an 88 Dana HP 30 also, it has the smaller joints.
I use the 88 for off road, and I want the stronger shafts in it.
If my 01 has the good shafts, can I swap shafts from a LP 30 into a HP 30?

Yes on all counts. Only the axle seals may leak on the '01 due to the smaller dia. shafts in which case you'll have to replace the seals using seals from the earlier model XJ.