A Lot! That low would probably involve chassis notching at the rear.
The front has maybe been converted to an IFS with airbags,nice truck though.
Those are some big wheels too,I like the big diameter with the old school look.
Here's
my low truck..... 
I forgot to measure the ride height before I did all the work.
So I don't know the total drop!

Oh and by the way...Welcome to the 'bolt. You might want to check out the picture posting policy.
(I see Cletis has sorted that!)

Jock