The elocker will go into the 90 housing, but it's going to be a couple of inches narrower than the 96 and up. That could easily be made up with wheel spacers though.
As far as modifying the 8.4 housing for the elocker, I think your out of luck there. Unless you have the tech to be able to cut off the mounting flange for the 8.4 and weld in a new one for the elocker. It would have to be pretty perfect though, as far as depth and alignment.
You can modify any of the 8" 4cyl housings to accomadate the elocker.