Z'ing the rear?????

[bigo181979]

I know a lot of people are running step notches but I dont like the look of all the stuff sticking through the bed. I want the floor to be flat like stock.
So my question is has anyone had any experience doing this???? What I am looking to do is like what they did on that fesler built truck that was in truck builder mag. Z the rear and raise the bed floor. Just looking for some guidence and I am z'ing the front 3" as well.
Here is the link to the truck I am talking about:
http://www.feslerbuilt.com/1967ChevyTruck.htm