I've driven a 258 I6 with 130,000 miles on it every day for the last 2 years, so it's strong if nothing else. The main problem is the carbuerator, it WILL cause you problems, if nothing more than making it hard to pass emissions. It does have a lot of low end torque, but the carb sometimes has problems with steep inclines and high altitudes. And it chugs gas. I look forward to the summertime, because I get a whopping 15 miles to the gallon instead of the wintertime 11 or 12 (oxygenated gas) I love my Jeep, but I would hold out for the 4.0 if you can.
I agree with Mike..hold out for 4.0 if you can. My Jeep has a 258 with 210,000 kms and it works fine except for the carb. I get a little better gas milage than mike...about 18-20mpg. I'm forever adjusting the idle...it is very tempermental. A friend of mine down the road has a 91 with the 4.0 and it works twice as good as mine. Seems to have just as much torque. Knowing what I know now about Jeeps (which isn't much ) I would have tried to get the 4.0
90 YJ...Stock for now.
74 Dodge Dart Sport
the 258 produces it's torque at a much lower rpm than the 4.0 that's it's big benefit...because of the longer stroke....adding an mpi or any fuel injection to the 258 will incease reliability and mileage.
89 yj w/ mopar mpi and 4.0 head.94 ax-15 tranny and t-case, more mods comin.
mellow , go to 4x4 auction store .com or jeepbay . com and hit auction . there is a 90, 4.0 HO rebuilt w/16k stage 3 mopar prfmce kit . w/92 intake mfld w/ injtrs and 92 distr. w/ wire harnse. the max price posted is $550. , there is only one bid as of 6/21 , of $100.