Check to make sure that there is not a hydralic cycinder on the engine side of the firewall or a plate under the floor where it may be. If so you have a slave cyclinder that works the clutch. Make sure that it has plenty of fluid in it. It is self adjusting.
And the manual type if you get under the truck and have someone push the cluth you sould see a linkage moving neer the front of the transmisson on the drivers side. There will be an adjusting rod on that linkage make the linkage longer and the cluth peddal disengages the cluth sooner and shorter helps it from slipping. If that don't work you may have to put a new cluth in the truck