Front bumper install, what's missing?

[Leinhit]

1960 C10
I'm trying to get my front and rear bumpers installed after repainting. However I get one step forward and two steps back.

On this front bumper I ordered brackets shown in one of the photos. But there's only two brackets and there's no way that will hold the bumper up.

You will notice in one of the photos it looks like the front of the frame has been cut un evenly both sides. Is something else supposed to be here to Mount bolts to through the bumper?

Obviously the bumper has additional holes for mounting bolts but nothing for it to go into. I have been looking for a close up photo, video,etc without luck.

If you have a specific picture / website/diagram for me to study I would appreciate it. What do I need to complete this and where do I get it?