Do you have a 2-door or a 4-door JK?
Any car seat should fit just fine, especially if it's just one. If you have a 2-door of course it's going to be a lot harder to get into the back seat, but it will still work. It's when you start trying to fit 3 car seat that you'll find things won't work. But with one, you can fit any carseat you want honestly.