1969 Dodge Dart GTS: How to remove rear exhaust hanger to replace

Lord Sparky said
What kind of tool can I get through the frame holes to grip the 1/2” bolt (the rubber exhaust hanger right before the exhaust tip hanger) to keep it from spinning to get the nut off? There is an access hole in the trunk but it is not directly over the bolt.

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All done! Used a jig saw to cut off the bolt. A little tricky getting the new bolt in with my fat fingers but I persevered.

Thanks for all your suggestions!