Hai I have a suggestion to make it clean...
Blend these two boxed regions (so add putty and sand/file to make the rear flared fender seam into the sheetmetal under the light and then make it match the same way with the corner above the light. The bottom part, with the bumper, needs to be on it's own on a different "plane" if you will.
If you do it right it could look really clean and have a fat wide rear.
