I knew about the exhaust spacers but I would need drive shafts too on the 3.5 (even if I'm not a huge offroader)..... yikes
It is recommended. Required on some years.
This is from their site FAQ.
On all pre-2012 JKs equipped with automatic transmissions, you will need to replace your front driveshaft with a narrower unit.
On all pre-2012 JKs equipped with manual transmissions, you will not need to replace your front driveshaft.
On all 2012 JKs equipped with automatic or manual transmissions, you will not need to replace your front driveshaft.
I can't say for sure if you will never have to but from some people I've talked to when I was looking into it, they strongly recommended changing it anyway. Someone here should have much more experience than I could answer better.