the booster springs you are refering to are called (overload springs).
they will only raise the height of the vehical the thickness of the spring itself.
these are made to compinsate for a load in the box of the truck to keep it from saging.
What you want to do is just add a leaf spring.
Go to a junk yard and buy two springs. preferably the first spring after the main ( the one with the bolt holes in them).
In most cases you can add this spring without changeing the U-bolts.
this will raise the rear the thickness of the leaf and then some.
There is a guild stud that bolts these springs together and it would be a good idea to have two of these handy when doing this job.
Also, the U-Bolts may strip out when removeing the nuts.
replacments can be found at most auto stores. haveing a set of C-Clamps handy for re-clustering the springs is a good idea as well.