Lift on an IFS vehicle can happen two ways.
First, everything can be moved away from the frame X inches to achieve X inches of lift. Trailmaster started this way back in 1986 with their 4" kits for Toyotas. It worked great, the lower control arm and diff were dropped 4 inches with brackets, and the spindle was replaced with one 4 inches taller. The upper control arm stayed where it was because Toyota routes the torsion bar into the upper arm. All of the stock geometry remained, and the only thing that changed was the driveshaft angle from the transfer case.

Here's my old 88 with the Trailmaster lift...


This is tricky to do with a Nissan (or Isuzu) because the torsion bar is mounted to the lower arm, and it requires that the back end of the torsion bar be lowered as well, puttin git in harms way. Trailmaster does offer a kit for older Nissan frames.

The other option is to change the upper control arm and preload the torsion bar (what all the Xterra lifts do). This causes the arms to be at a steeper angle at static ride height, thus creating lift. The new upper arm is a different shape than stock allowing it to not touch the bumpstop as the stock arm would at the same angle. This gives the suspension more overall travel, but only by adding droop. Upward travel limit remains unchanged, which is why the compressed length of the shock must be the same as stock.

The trick with the Xterra is that the stock shock is very short. It has 4 inches of travel but needs to be 8.625 inches long compressed and 12.4375 inches extended.

By going to a longer shock, with say 5 inches of travel, you run out of room in the shock body for the piston.

The best solution is to remove the upper shock mount, and replace it with a taller one, and run an overall longer shock. Still waiting for someone to release a bolt on, or weld on kit to do this.