I think your going to have problems using anything that is thicker than the stock plate, which is about .090"-.095". The diff bulkheads and the upper and lower front and rear plates sandwich the framerails main chassis plate and plastic spacer/mount block for the front and rear assemblies. If you use thicker material it won't fit inbetween the upper and lower plates of the suspension assemblies. I'm probably not explaining this very good, but take a look at how the parts stack together on the truck.
http://s68.photobucket.com/albums/i2...adspics003.jpg