1968 Dart Trans Swap
I would recommend tat as much as possible all corners are filleted (curved) to prevent a stress point that might start a crack in the floor down the road.
I doubt the OEM did but they needed to build in "designed obsolescence"
Might be overkill but if you can why not.
" Ounce of prevention..."
Don't mean to through you under the bus Pntastar69. Your photo was handy.