I need stiffer front shocks

[my new 72]

I am having trouble with my wheels rubbing on the inner fender wells when I hit bumps. The shocks on the truck are crap, they have way too much travel. My truck is lowered about 5 inches up front and I am running 255/55 18's. What do you guys recommend as far as an adjustable shock that I can adjust to the stiffness I am looking for?

Edited to describe problem better: When I am driving and hitting normal bumps it is ok, but when I hit a large dip in the road, or a seam in the highway that has created a large dip I get wheel rubbing. This does not happen over normal bumps, my shocks are just worn out and I am looking for some stiff adjustable shocks to get a stiffer ride. They can have 15 inches of travel for all I care, I just want to be able to limit it with the pressure settings.