They were all dirty or cracked bushings, definitely failing state. I've only went with window weld if was too lazy to take things apart, though nowadays window weld is pricier than getting replacement bushings.
I did have one that needed extra stiff bushings, so used concrete leveler. Needed to make molds to pour it in, but it completely filled the voids after some days of curing. It was definitely close to solid, had to tap it in with mallet. Car already had stiff cusco style transmission and engine mounts, so a little more noise from solid diff mounts isn't an issue. It was $7 at home depot.