4.5 or 6.5 lift? 99xj
 

I want to go to a 6.5 but will I need to get new drive shafts?

You'll need to do something with your steering, you'll wanna run control arm drop brackets at the least..at that height you should be on long arms..you will need a slip yoke eliminator...and will have to get a cv style rear shaft.

And 6.5 is kinda tall...why do you want it so big?

Well it's my first personal build. I've had Xj's before but I bought them already lifted. I ran 33's and with cut fenders I was still cutting my tires when I flexed.

cut fenders more or add bumpstops. 4.5" is a great height. that being said my rear sits around 6" with the shackle relocation. the rear driveshaft with SYE is a perfect fit. if that's not long enough you can try to find a junk yard ZJ driveshaft that is longer, or worst case just go to a driveline shop and have them retube and lengthen for a couple bucks. no need to buy a custom driveline. you WILL need an SYE though