If I buy this will I be able to use a front drive shaft for a rear with no other modifications? Thanks in advance. I'm new to the xj world..

 

I assume that is a "hack-n-tap" SYE.
If so, then the answer to your question regarding the front driveshaft is "probably".
But there are some other questions. How much lift do you currently have,
other modofocations to the suspension?

Also, regarding your question about "other modification".
Installing that SYE requires modifications all by itself, i.e. cutting off
a portion of the end of the output shaft on your transfer case and drilling and tapping an accurate hole in the end of said output shaft.
Also, you will almost certainly have to shim your rear axle to adjust the pinion angle to point up at the transfer case, which
is different than the current angle, which is, most likely, pointing parallel to the transfer case.
I hope this answers your questions.

 

That is a slip yoke for a stock rear drive shaft, so no.

This is a slip yoke eliminator to run a front ds in the rear
HD Slip Yoke Eliminator (NP231) - Iron Rock Off Road

This is a Hack and tap style SYE so you could run a front ds:
Hack 'n Tap Slip Yoke Eliminator Kit - Iron Rock Off Road