tropical36 wrote:
Get some recommendations from a truck shop for beginners.
This is very good advice. You should be able to find a frame and chassis shop not too far away in most areas. (I know of one or two around here at the opposite corner of the country, but that's not too helpful for you.)
If your rear suspension is riding lower than it ought to, air helper springs will help some, as would installing an additional leaf or helper spring. If it's riding low because something is broken, obviously that something should be fixed.
If it's just a somewhat poor design with a lousy departure angle, you can maybe gain a little bit with suspension upgrades/fixes but to some extent you're stuck with what the builder put together.
I have ride-rite air helper springs on my class C and for me they work quite nicely.