You just sleave longer bolts through the same mounting points. ie. If your lifting the body by 2" you will need replacment bolt 2"'s longer than the originals. Then use box section or tube to sleave the bolts. Basicly standing the body on stilts over the chassis. You should weld a plate about 3-4" square on the top and bottom of each box section / tube, to spread the waight. Once the body is bolted in place weld the bottom plates on the box section / tubes top the chassis everywhere you can get at them.
Remember depending on how high you are going yoy may need to replace some wireing and break piping to reach between the body and the chassis. Also the stearing linkage may need extending.