These rear suspension bits for the 58 were a low volume item and Ford was the only manufacturer/supplier of them. Now, 52 years later the NOS parts have dried up and some specialty houses have made complete sets, Rare Parts being the only one I know of. Over the past 5 years I have heard from 3 individuals who said they were going to make their own and several sets for me. None have been able to do so. I've provided samples and even the special sized tubing to bond the rubber to, but the projects have died on the vine. I know their cars are still being restored and they may get to it someday.
One solution I've heard of is to take a bushing catalog where bushings are listed by size ( I believe NAPA has one, and possibly Flagg has one) and find a bushing that resembles the correct one and modify it to fit. Another is to bite the bullet and pay the price to someone who has invested the resources in creating the correct ones.
The bushings in the link that Anders needs never were sold separately, only the link with the bushings was available. I believe a good mechanic could figure a way to make an existing bushing work.