4" axle with 3" drop mono leaf. The mono leaf dropped it more like 3.5". The rear has a flipped axle a monster notch and is loaded with concrete at the time of the picture. I will be adding a mono leaf to the rear that should put it a little lower than the picture with no load in the bed.
If you want to do the mono leaf and a 4" axle you will need a steering arm kit from
http://www.droppedaxles.com/CHEVY_AXLES.html to flip your drag link and you will also have to move your brake line upwards on the frame so the drag link bolt will not rip the brake line off when you hit a bump. Here is a picture of the moved brake line so you can see what I am talking about. You can see the stock brake line hole just below the new location.