Subframe connectors
I'm a little surprised by this.
Mine went in a '65 Dart with no problem. They come through the floor behind the driver's seat and enter the front of the rear sub. I used 2 X 3 X .125 wall and tied the floor to it as well. Where in Wisconsin are you ? If you're close to civilization ( Mpls. St. Paul ) you could swing by and see how it worked on my deal........your floor ought to be pretty similar.