Lift blocks will get you no where, 1st gen Xterra mild front lift is free.99, just need to reindex the torsion bars for 1.5" of lift, over 1.5" you will need new UCA to maintain a decent ride. For the rear you can do shackles or AAL, either will normally get you about 1.5" of lift, sometimes more sometimes less, all depends on the condition of your rear springs.
Also, installing lift blocks on leaf springs is bad news, even though it's cheap, it's really a poor way of lifting and wears the springs out from axle wrap.