A late model F350SRW squatting 3" in the rear should put the truck fairly close to level. If headlights blinding other drivers is your only complaint, you can re-aim the headlights down a little with the adjusters. :)
Does your trailer have any height adjustment at the axles, in the spring brackets/shackles? Some have multiple spring eye bolt holes so the springs can mount higher or lower, to raise or lower the trailer.
You can also do a spring-over-axle conversion on the trailer, which usually raises it about 4-6 inches. Then, adjust the pin box lower, or hitch higher, to level the now taller trailer. The spring-over-axle conversion mounts the springs on top of the trailer axles, instead of underneath. This is commonly done with fifth wheel toy hauler trailers, being towed by tall 4wd trucks.