When you change the shocker bracket be prepared for the vast rust hole that will appear under it when it's removed.
Then it's welder out time.
All of a sudden a simple shocker mount change turns into a 20k refurb!
If you have a welder.................................
Those 4 little setscrews are very easy to shear off. I disconnect the alternator, clamp the earth from the welder firmly to the body and substitute the welding rod with the carbon rod from an old C or D Zinc / Carbon Cell.
I hold the carbon on the head of the set screw and switch on the welder for just long enough for first the carbon and then the screw glow red hot.
Apply 'Plus-gas' when things cool down.