I modified my motor mounts today which required removing then reinstalling. Removal as the nut spun I just torqued them around till they came out and dropped the nuts in the frame. Which were then fished out with a magnet.
Install on the other hand would be easy to get a hand in there....if the lower A arms were removed. Otherwise access was a small oval hole in the front of the cross member.
So what I did was put duct tape on the box end of a wrench and then reached way in there through the slot to line the nut up with the hole so I could get the bolt started. Worked great!