When I installed mine in my Cuda, I did have to mod the bracket alittle.... the holes didnt line up very well and the base flange was too wide to fit in the space I had. So I have to take a cut off wheel and file to my $60 brand new mount...always fun to hack on brand new stuff
I did talk to FR before I cut it, to see if I had other options, but there werent any. I considered trying to use the stock bracket too. I would call them rather than email..... much easier to talk directly about this stuff, than email back and forth...plus quicker...
So by the pix, I assume the "O" goes up into the "pocket" in your dash? Mine hung down, so the base width was the only issue for me. From the pix, I also assume that the issue is the "O" portion is too big to fit in the pocket?
Flaming River does have several different mount kits....have you looked at their website to see if any other will work?
If not, then you will either need to modify the new bracket to fit the opening or the opening to fit the bracket. Your choice....