What's the difference between the cages if any? I'm looking at buying one from a 4thgenner and want to mamke sure it fits.

 

Debatable. Depends on the exact style of the roll bar/cage. Some of the interior may be different enough.

It doesn't really matter though. Since the rool bar/cage needs to be custom installed, the differences between a third gen and a fourth gen may not be enough to cause a problem.

The price of a kit isn't very much. The higher cost is in the installation. You can pick up a kit through Jegs or Summit for a couple of hundred bucks. Typical installation costs are $100-$150 per point.

It's called a cage if it includes a halo bar and a-piller bars. If it only has a main hoop and forward/rearward/tranny tunnel bars, it's only called a roll bar.

 

It's the Jeg's 8 point roll bar. Different p/n so maybe it won't work.
thirdgen = 550-940303k
4th = 550-944503k

Thanks.