I assume this is a 90 Toyota mini truck from your nick.
It’s probably and optical allusion. The rear wheel opening is lower then the front. Measure at the rockers to see if it’s really sagging. Here is a picture of my truck with 33x12.5s no lift at all and it really is sagging a little in the rear but not much. Just the cut of the wheel opening makes it look more then it is.
If your truck is like my 86 4Runner it has pretty poor suspension travel in the rear. A 1-2 inch suspension lift wouldn't hurt it at all.
The IFS front is a whole different ball game. Its best the keep the IFS in the center of its travel. "Cranking the torsion bars" will run the truck up some BUT it will affect ride because you will loose wheel travel. Some of this can be over come with a Ball joint spacer (
www.4crawler.com) that will increase wheel travel. BE CAREFULL. If you "Crank it up" you are running the CV's at a steeper angle and it will shorten their life and cause the boots to fail early.
On my truck I plan to 2 a 2 inch body lift from 4 Crawler, ball joint spacer, longer rear shackle, 2 inch engine lift and a custom cross member. Once I get my Clocked Marlin it will give nearly 6 inches better clearance at the transfer case cross member over stock. The 4 Runner also has a low hanging tank and that will allow it to be lifted 2 inches as well.
So at the center of the truck at its lowest point with a 1 inch suspension, 2 inch body, custom crossmember plus the extra height of the tires will net you a minimum 7-8 inches at the cross member (break over point). If you are not up to the cross member fab
www.buddbuilt.com has a nice set up for a reasonable price. Just make sure you tell him you did a drive train lift and he will get you the set up you need.