I think you need to diagnos the whole front end. Jack it up, put it on jack stand and make sure it is stable and high enough to let the axle hang on the springs with the tires off. See if the axle moves back and forth. If it does you need to replace the spring shackles. With no tires on you can see any movement of the spindle to the axle and answer your kingpin question. Also a good time to grease the wheel bearings and make sure they are good and adjusted properly. I believe, but have not done this, you can tighten up the ball connection on your tie rod ends now as well. From your tire wear, it sounds like you need to set your toe in too. I think you can find the specs in an online manual. I have done using a tape measure, but it is best to have it done professionally once all the other stuff is fixed. While you are doing all this, you might as well adjust your steering gear box too. The shop manual gives some fairly clear instructions. I remember using a fishing scale to test for the proper pull during the process. If you do need king pins, they come in oversizes but usually require a trip to the machine shop for reeming and sizing. None of these task are overly difficult, but all of the components need to be up to standard to fix the front end. When they are all correct the truck will drive like new.
Mike
