I have a 90 xj and I've been searching around looking for a poor mans lift kit and I came accross the Rubicon Express 2" Standard Lift Kit . which looks to me to just be blocks front and rear and new shocks.. my thought is Sense I have access to a welding and repair shop that I could make the blocks myself and buy bolts and shocks from the local parts store cheaper and quicker then buying this kit and waiting on it to be shipped to me. I'm wanting to get 4"s  of suspension lift or atleast be able to fit an agressive 30" or 31" Mt (33" prefered) under the xj. But I'm conserned that 4"s of blocks is either going to cause other problems with other things needing modified to reach and fit where they should or that 4"s of blocks is just going to be to unsafe. And I'm not real sure how to go about making the blocks or if I make 4" blocks does that translate into a true 4"s of lift? so yea I'm kinda at the cross roads of risk it or give up on the lift all togeather. so any advise I could get would be great thanks  

you can only block the back  

piney is right
also may I add at 4" some would recomend a sye and extended brake lines so keep it simple at 3" custom blocks with a small axle shim in rear to keep dlines in check have fun on some 31 the rear is simple the front on the other hand is not cheep to get that 3" could I recomend some trusty pucks but I would realy recomend saving your beans and geting a better or best lift kit from a trusted manafacture you much happy with the performance hand down  

That is a coil spacer for the front and an Add a Leaf for the rear... it's a good choice for a small budget lift.  

I run 34's with somewhere between 6-8" of lift with no SYE, just a limiting strap attached to the center of the rear end, to stop over extention. No problems with that.