'73 Dart Swinger Bumper help needed!!

Have we tried bolting the brackets to the car first...loosely. without the bumper. and then holding the bumper up to the brackets?

Fyi this is probably irrelivent...but my 74 had the round shock style brackets. Not ones like u pictured. I still have the original 74 bumper. If u need me to dig it out and measure mounting holes, or photograph the rear mounting studs.