The upper strut nut is rusted to the mail thread. How do you keep the inner assembly from turning when you are turning the nut? I’ve turned the nut enough turns to move the nut at least 3X the engagement lenght, and it’s still showing the same number of exposed mail threads. 1995 DeVille, rear, both sides.
I’ve always just used a nutbuster and busted the nut off. A nutbuster is an inexpensive tool that has a hexagonal hole for the nut and a wedge that you can drive into and split the nut. The wedge is driven by a screwjack mechanism. Its use is obvious.
Or, you could cut the nut off with a dremel tool.
I like MB’s nutbuster advice.
I’ve often used a pair of vice grips on the strut shaft - reaching in between the springs to access the shaft.
I remember the vise-grip on the shaft working well enough.
If the new struts came with replacement nuts, then yes, just dremel off the old nut.
If they did not come with a replacement nut, then see if you can get a replacement from Napa, or something similar, then dremel the bugger off.
You’re better off not wasting time trying to save this nut.
It will ruin your day.
I just have to say it since I’m thinking it - you do have an appropriate spring compressor tool on there right?