[ChevyRacefan]

I would use a plasma cutter, if metal bumper.
The problem is, chrome bumpers with exhaust running through them rust, the O.E.M'S tried this.
With painted bumpers the heat discolors the paint.
I don't think it work with a work truck step type bumper. like the o/p photo.
But the sport type bumper it look good, or roll pan. It is your truck build it the way you want.
If a Chrome bumper, I would cut it with a plasma cuter, in steps, keeping down the heat in the bumper. cut 1/10th of the hole stop and blow compressed air on it to cool it. then another 1/10th. Grind the whole smooth and then coat the edge you cut, with high temp paint.