'00-'05 rear strut repair problem

I developed a "thunking" noise on the rear passenger side and narrowed it to the cup or upper spring pad. I removed the strut assembly and compressed the spring. I attempted to remove the upper nut holding the shock with a wrench and a vice-lock, as is usually done. The gripping area above the nut broke off, however.

I need to remove the shock. At this point, I'm fine with destroying the current shock and replacing the rear pair. They look like original equipment which means 50K and 18 years!! So basically, I'm looking for advice on removing these corroded in old shocks. My 2 foot bolt cutters are not large enough. Hack saw? Do I need a cutting torch?

The actual vehicle is an '02 XG350, but the rear strut assembly is identical to the Sonata, so I decided to ask here for a larger community.

 

Have your tried ... grinder?
Please think about letting a mechanic do it for you

 

Success!! I had to use an angle grinder with a cutting wheel to cut off the shock nut. On one strut assembly (the one making the "thunk") the foam rubber bushing was totally rotted away and I could cut the shock absorber's shaft directly. On the other, I used a grinding wheel to get down to the washer. For some unknown reason, Hyundai used foam rubber for the shock mounting bushings. I'm surprised they didn't give out long ago. The industry standard, and the OEM Hyundai replacements are made of firm, solid rubber.

Now I'm hoping to tackle the hopefully easier issue of some noise I've narrowed to the power steering belt. I'll post more on the issue in the XG/Grandeur section, although it's probably identical with a V6 Sonata.

 

Good news.
Thanks for the update