Mechanics apply with in

There are 2 different 4.0 motors.....one is a cam in block which is much easier to do head gaskets on.

The other is an overhead cam 4.0 This one has timing chains on the front & rear of the motor, and some genius designed the cam shafts and jack shaft so that there are no key ways, and no way to line up the timing marks because there are none! You need a special kit that attaches to the cams and crank pulley to set the cam timing.