How do I install the bed on a 2004 Dodge Dakota

Where the frame meets the bed directly you should need no rubber or shims. Some beds have raised areas that need a bushing to fill the gap between the bed and frame but most need nothing. Body shops do use shims on beds to get them level if there have ever been any accidents, the frame is out of plum or the bed is not level. So if you get it on and it is too high or low an any certain area just shim it up till it gets where you you want it and looks level and fit.