Do a search for a Mitsibishi Starion diff conversion. I haven't done one myself, but I'm pretty sure there is helpfull heaps of info on this site. You would probably end up with disk rear-end too!!
There are heaps of mitsuishi ratios. L300, Pajero, Starion etc. I'm sure one of them is 4.6:1
The Pajero diff might even have a lsd option.
Let us know what you find in your research!!