this is a lot easier said than done....the only reason i know this is because a buddy of mine and i were considering doing this same thing to his yj.....
first you'll need to change out your axle setup by either grinding off leaf pack perches and rewelding coil perches on, along with control arm mounts and shock tabs.... OR just get a set out of a tj and just swap them in....
then you'll need to address the coils and if youre going to run stock setup or go bigger.... bigger is a deffinate with this swap anyways just because...
if and when you run a 4.5" or bigger lift i would seriously consider long arms for controls arms becasue the ride is so much better and you'll get better performance out of the rig anyways....
this address' where you will have to mount the control arm mounts on the unibody... this is again easier said than done... welding to the unibody is risky at best considering it's such thin metal... a bolt on kit from just about any lift kit provider is your best bet....
you will also want to make sure that your driveline matches up to the setup... if you use the factory axles you should be fine...just check your drive shafts with the swap or not for any issues with length or any binding that could occur....
also if you swap in a set of newer axles double check the lug pattern on the wheels because they might vary slightly....
there are a lot of issues you can run into when doing this swap so just be sure to plan ahead and weigh every option considering if it is going to be a mall crawler or a true 4x4 seeing dirt every weekend or so....
hopefully this will help a little and not throw you to the wolves.... if you have any questions just let me know and i'll try to help out as much as i can!!!!
CHEERS!!!!