Im not at home to get the correct hole measurements but:
If your mounting like I did just measure the holes in the smoker body where the bolts for the rack brackets are. I mounted mine using these existing holes for the handles. Just measure center of hole to center of hole and it will get you a measurement. If you are mounting horizontal you can make the holes close to the handles sizing you make. The key to remember is bend the flat stock closely to the handles measurements or it wont sit in the handle flat. Its better to get this part bent first and then bend the tabs for the handle mounting points.
The flat stock I used was aluminum stock that was 3/4" wide. Its slightly wider than the size stuff Weber uses but fits the handles okay. I had to file a hair off the edge in handle corner area but was easy to do. I used aluminum to make it easier to bend and no worries about rust down the road..
