The stock front shackles on our truck were thrashed, probably from lack of regular lubrication. I searched catalogs ond web sites like "energy suspensions", but had no luck finding urethane replacements. They don't like to tell you the dimensions of their products
So I bought some Delrin rod. Delrin is a plastic like hard teflon. After a couple of hours of work on my brother's lathe I had a new set of bushings. The truck has not been on the road since the modification so I can't tell how well they are wearing, but this is tough stuff.
In the rear, I am using springs from a Blazer, so I am using urethane bushings from "Energy Suspensions"