Is it lacking power for your liking or is it down on power for a 258? If you want to get good power for a 258 there are options to look in to. If you want good power in general then you will most likely need a V8. You have to remember that these engines stock put out around 115 HP give or take depending on the year, however, torque was over 200 ft. lbs and at a nice low RPM. A nicely modified 258 can be fun with decent power and torque but you are not going to get whiplash from hitting the gas pedal. A better carb and exhaust will wake it up a bit and give you some power you can feel but it isn't going to be a huge increase, even a 20% increase over stock is only going to get you a little over 20 HP.
Take a look at your ignition system, there are many options that will give you better performance and driveability. TFI or HEI upgrades are common as well as MSD upgrades. Make sure all the supporting systems like fuel delivery and spark are operating correctly and you are getting the most out of those. If you can't find the power you need there, you may need to dig into the engine with a cam or head work.
Plan out what it is you want and go from there. If you want V8 power than a V8 is what you need. If you want a nicely powered 258 than start modifying with an idea of where you want to end up at to make sure everything works well together.
My engine is decently modified and runs strong. Compared to a stock 258 it feels like a V8, compared to an actual modern V8 it feels like a six cylinder. Hope that makes sense.
'85 CJ-7 - 258 bored .030 w/ mid level cam, 4.0 head, Clifford intake and header, Weber 38, TFI w/ MSD 6, Black Diamond 3" lift, Daystar 1/2" lift shackles, 33x12.5 Goodyear Duratracs with stock 3.31 gears.