Wow, this is a tough one to sell. The problem, as I've been told is that the 4.0 doesn't just bolt in, even if u get one still attached to the tranny & transfer case. Motor mounts have to be fabbed or removed & replaced, new ECM, etc. if you're determined to keep that YJ, you might start with new gears and engine mods (intake, exhaust, throttle body, snorkel, etc), or I would consider swapping for a V8 or a 4BT diesel. The 4.0 is pretty stout, but unless you have a spare drivetrain sitting around, the cost of all those mods and labor will quickly surpass the cost of simply selling your Jeep and buying one with a straight 6. If you're swapping Jeeps, look around a bit and find one that already has the V8
