How to drill a 3/4" or larger hole in a steel bracket?
If you're referring to the hole at top center in your photo, you'd have a hard time drilling a new hole halfway overlapping an old hole. A better approach would be a rotary grinding tool. Any abrasive grinding bit will allow you to enlarge the hole enough to get the bolt through. 

Be aware that this will tend to heat the part being worked. A damp rag on the part near the hole will absorb heat and prevent paint damage. 

Alternatively, clamp a scrap bar over the original bar and drill through both. The scrap bar will act as a drill guide. You can use any high-speed steel bits available. There's no need for titanium or other exotic stuff.