Metal bushings, without a doubt or second thought.
As for the tilting tires issue, no it is not good on the suspension, tires, or the kingpins/wheel bearings. It makes stuff wear out faster for one, and it does affect the handling of your truck.
Your springs might be worn beyond usable strength, as well, so that might be something to look into. They are relatively inexpensive, and worth the cost of replacement on a 35+ year old truck, especially one thats been used hard.
To test for king pin problems, take the wheel off so you can see clearly the entire spindle area. Now grab the top and bottom of the drum (or rotor) while it is still properly installed, and try to push-pull in opposite directions with your hands. If the entire assembly is moving on the i-beam, it will be noticeable behind the hub assembly. If it is the wheel bearings loose, just the drum/rotor will move ON the spindle, but the spindle itself wont move.
Edit: You mentioned not having an auto shop there; assuming you mean a machine shop or mechanic?
Those kingpin bushings will need to be pressed out, the new ones pressed in, and then they need to be reamed (cut) to fit the kingpins. Unless you can find someone who can do this, you're likely going to have to send your spindles out somewhere to get this done properly. It's not something the average person can do well without the proper tools, but it can be done, if you want to try tackling it.
