There's a recent edition of HyperRev's Impreza magazine that has a 2 page article on the things needed to do to convert a bug-eye to a cross-eye; I imagine these pages will be somewhat useful for you in doing the reverse. Once concern I have is the front clip around the headlights; iirc, for a bug-eye to cross-eye conversion, some part of the front clip near the headlights need to be trimmed. For the reverse (like what you're thinking of doing), you may need to trim other areas. I also recall seeing a photo on one of those pages where the fender of the cross-eye mounts slightly differently. For the bug-eye to cross-eye, the HyperRev magazine's solution is to place some washers and the original bolting point works quite well. If this is a must, I'm afraid you'll run into problems when trying to install the bug-eye fenders onto the cross-eye.
I'll see if I can find some pics off that magazine.