Cutting that brace out was an old time trick to get the 4 speed linkage to clear the floor pan on cars that didn't have the 4 speed hump. A good friend bought a 70 Challenger many years ago and shelled the clutch in it. He called and asked if I'd help him put in a new clutch assembly and flywheel. I went over to his house taking my trusty floor jack and stands. We set everything up and as I jacked the nose of the car up on the K member, both doors popped open. To my surprise, that brace was cut, the car didn't have subframe connectors and there was no 4 speed hump in it. As soon as we got the new clutch in it, I told him he had some serious work ahead of him to get the car straight again. After a stint in the frame shop and welding in a piece to the brace and installing subframe connectors, the car no longer sagged when you jacked it up.