You very most likely have the 258 as already stated. Between the #2 & #3 sparkplug wires you will find a machined pad with stampings on it. THAT will tell us what we need to know about your engine.
If you want to know even more about your Jeep, if you can, take a look at the rear axle at the differential on the right side. Right where the tube meets the pumpkin on the rearward side of the axle the is a letter or letters stamped onto the housing. That letter or letters will tell us what gear ratio was originally installed into the axle. There's really no way to know exactly what you have now without counting gear teeth, but chances are good that the stamping will be correct. If we know what's stamped, we can take a look at whether or not spinning the drive shaft and wheels will come out at a similar ratio. (this sounds much more difficult than it is.)
Be kind. If for no other reason, it will confuse the daylights out of people and make them wonder what you're up to. And ALWAYS drink upstream of the herd!