Back when I used to have a G-body Cutlass, I re-did all the suspension with Polygraphite suspension bushings. They had a bunch of marketing claiming they were better than regular polyurethane bushings because they had graphite impregnated in the bushings, which basically made them "self lubricating" so they wouldn't ever have any squeaks. And as long as I owned the Cutlass, I never
did have any squeaks. I bought the whole kit from Performance Suspension Technologies,
https://p-s-t.com/
I've been thinking about buying a full suspension kit from them for my Burban.
Their kits are actually a good bit cheaper than pricing out all the parts separately.