Help on bodylift

Started installing a bodylift on a 97 yukon 2 door. Completed all steps up to adding the body mounts. While trying to lossen the bolts I found 4 out of 10 to be frozen. Any idears as to how I can get them off? Has this happend to anyone before?

I had a couple hard ones on my s-10. I chanced it and took a breaker bar and a pipe and got em loose. the other way is to sacrifice the factory rubber body mount and heat the bolt up with a torch. It'll come out with heat. The downside is you have to replace the factory rubbers. Not necessarily a bad thing!