man, why even swap out the motor?  the 4.0 in my mom's grand cherokee has gobs of torque.  i personally wouldn't run a toy tranny behind a big, fuel injected chevy motor though

you can run a 150/151 behind a 4.0 without any adapters though...look in the "5 speeds" thread in the suggestions section.  personally i'd run something like an NP435