Fortunately I was able to drill into the bolt after many attempts and it spun out enough for me to grab each side and turn it counterclockwise to back it completely out w/o damaging the welded nut above the hole. I then replaced with M8 nut per M. Haibeck suggestion and it screwed right in no issues. As your indicating there is zero access to that nut as it?s completely enclosed by a rectangular metal frame. M Haibeck states he often drills a small hole next to where the bolt is at on that frame to spray rust buster prior to removing upper mounting bolt to prevent what happened to me. Apparently he has a way to weld a nut in that space but it is a prolonged time consuming event as he related to me.
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