My straight 6/242 has seen its last battle and I now am in the process of re-building/replacing a lot of different things on my Jeep to include the engine and possibly the drive train. My question is I have access to a straight 6/258 and was wondering if I could drop that into my '91 Cherokee with the AW4 Trans?

Has anyone done this and if so is it a straight swap pull one out and drop in the other?

 

Gigantic can of worms. Find a good used 4.0.

 

Dont put Entire 258 into your Cherokee, only Part of it. Use 258 Crank and Rods with 4.0 pistons for a Stroker. Well Worth it, if done right. Go Low Buck and use the Factory Cam and lifters, then you wont have to worry about valvetrain problems.

 

X2, rebuild the 4.0 and stroke it. Or just rebuild the 4.0 without stroking it if you would rather do it that way.
Regardless, I'd keep a 4.0 in it, its a lot of work swapping engines.