The spacers are made of lots of different materials, usually steel or polyurethane, and usually are 2.5 or 3" for fullsizes. You won't break one. It won't happen. I believe they are interchangeable between ALL the fullsizes. Even the one ton. I have a 3" in my dually. On stock backspaced wheels you will be able to clear 35's no problem. Mebbe a little rub on the control arms at full lock.