Sounds like what I went through.

I replaced my rear subframe bushings and differential mount. I still get the "clunk" but not near as bad but it now drives tons better. I will be replacing the rear shock top mount bushings next.

I also replaced the guide rod mounts too. Now the front end feels tight. I used to feel it "flex backward / forward) " a bit just before coming to a stop and releasing the brakes.

I have two new guidrod mounts. I bought them then found a set of Lemforder brand ones. So if your interested in the Febi's PM me.

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1986 560 SEL
1960 Ranchero
1970 Cougar XR7
2002 Crown Vic Sport
1992 F150