Thank you guys for your feedback.
I first address BJCSC:
1. some I can turn back - but only with a 1/2" break bar. The bolts are 85% or even 95% unscrewed- I can not really see -the end of the bolt is inside the mounting beam.
2. yes. it is true. 3 out of the 4 bolts (2 per side) are preatty much stripped. But not the thread is stripped but the head (E-12 socket).
some I could screw back but not a lot.
Since this morning I tried to take them out - so far unsuccessfully. I still have tomorrow. Is there anything else I could try?