Keep in mind the FFR hood is a double layer with the strengthening ribs up the center. This is where most of the interference occurs. You can trim the ribs and move the reinforcement around the air cleaner in many cases. This leaves a "normal" looking exterior, but requires a few hours of work. Yes its tough to build in 2 separate stages for multiple reasons. Since FFR doesn't include any dimensions in the manual the task is mainly trial and retrial. Mine doesn't even have the original radiator so I don't have dimensions for the original grille. Sorry, somebody will come up with them.

Good luck!