Bump stops make a dig driffrence. There main porpuse is to make sure your tires dont smash your fender wells. There is also a set to keep your wheels from turning into your body panels.
I lengthen mine and put bigger bottom bump stops in when I put on my lift...at 205$ a peice for a tire I did not want to chew one up hitting the top of the fender.
What I did was with the tires off and the sripngs removed, the frame still sitting on the jack stands, I placed the axle at normal riding height (using two floor jacks).
Then I lifted one till I was able to measure from the center of the axle at the face of the hub to the top of fender well. I had to add over 2.0inched of spacers and buy a longer 10mm bolt to attach them to factory bump stop.
I did fail in adding the hypotenuse and sine angle height of the width of the tire.
So I did hit till I added 1.312 longer bottom bump stops as well.
This method is also good in telling you the maximum travle length that you will need for your shocks, when doing a custom lift.
This took about 2 hours and I was able to purchase the stock at a local salvage yard and drill and counter bore it at work on a lathe.
The bolt was a special order and had to come from a local fastener place that sells 10mm x 120mm long bolts.
I have since had to cut one side of the factory bump stop and bend it back 5 degrees and weld up the cut due to bending. it was hitting the coil spring and making a gowd awlful noise that took me several days to locate.