David,
In regard the electrolytic/caustic rust and paint removal, rather than post a lengthy description I would direct you to the many listings on Google or,
Morris Register of Victoria - Dissolving Rust
I used the setup on this link and found it thoroughly effective, just take note of the safety advice.
I note your use of polyurethane, which subject to the hardness used, may have some benefits over the standard rubber, namely it's resistance to oil and inherent strength. Unfortunately it still develops a compression set under sustained load and is unlikely to be any stiffer than the metalastic bushes used in the wishbone arms. I did use polyurethane on the sway bar bushes, as these were readily available.
I think it is apparent when you rebuild the front suspension, how much development Bristol have done on that system. If you look at the very rigid double wishbone and sway bar design, complimented by a coil spring that is seated on a range of materials - rubber and urethane for fine damping. No wonder it works well.
Best regards, Jason