Carl,
Rear heights vary a bit depending on leaf spring condition (sag) so on an unknown one you might cut wood blocks in various thickness to place between the saddle notched into the MII cross member and the bottom of the frame rail. The weight will need to be on the front springs to get the height right and if it's not it's easier to replace wood blocks than cut weld. With coil overs one has several inches of adjustment on the shock body but it gives more fudge room if cross member is close to desired position. Sometimes have to tweak a little after truck has been driven for a time and the springs settle, usually unevenly, but adjustable coil overs make correcting an easy task.
