I did this mod about a year ago, a bit deceived by the pictures I saw that appeared to show that the F30 scoop projected past the inside lip of the wheel. This isn't the case for even the OE 7.5" front wheel.
In any case, here are a few pictures of my installation that may provide some inspiration for others:
1) I marked the new backing plate from the opposite handed original with a transfer punch after first bolting the two together with appropriate spacers to keep things parallel.
2) At the same time the required trim for the caliper was marked.
3) As others have noted the required hole is tight up to a bend radius. I used a Roper Whitney No. 5 punch to make the holes rather than a drill.
4) The backing plate is very soft so I made a simple reforming die out of aluminum to reform the radius to accept a bolt and washer.
5) Here is the plate installed (I was changing wheel bearings at the same time). Note 4th bolt that most others don't use.
6) Using the 4th bolt requires making a suitable length spacer, and the bolt only picks up a half-hole. Regardless, it substantially stabilizes the backing plate.
7) As others have noted, there is some interference with one of the ball joints.
8) Here is the affected area.
9) I bumped this with a ball peen hammer on a shot bag.
10) The conflict is resolved with just a bit of reforming.
11) This is the view of the plate with an OE 7.5 x 18 wheel.
12) A more face-on view shows that the scoop does not project past the inside edge of the wheel.
