Miguel,
Here's another thought---
Get a good (not from Tiawan) combination wrench, and stick the box end
on the bolt, and smack the open end side with a small sledge----

If this doesn't break them loose, you've got big, mucho problems !!

Next solution----Heat wrench !!

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Terry--
74 Campmobile- (Clementine)
85 GL- (Delilah)
86 BMW 325 ES- (Eva)