Well, what is the backspacing on your current wheels? Do you like the stance? If you are going to keep the tires then you will need 15x8 or 15x10" wheels. If you like the looks/functionality of the profile on your tires now then stick with the same width wheel you currently have. You don't need to concern yourself with offset for a Jeep application. Offset is mostly applicable to cars. Backspace is the measurement from the inside rim of the wheel to the center where the wheel mounts to the hub. I'm not familiar with CJ's much, so Idk what the factory bs is, probably around 5", but it's easy enough to measure.
Hope this helps.