I tried it, and went with new uprights, Aarms, rear axle and fenders
I do have a ton more traction to show for the effort though... whereas before, I could blow away RA1s in 1st, 2nd, 3rd or 4th by simply rolling on the throttle, I can now only get it spinning in 2nd when the car hits the power band (ofcourse I can still easily get it loose on shifts). Part of that is due to more traction, other is due to going to 3.42 from 4.10 rear.
Having less traction IS more fun though.
As for your problems, for the rear fender, if you think shaving the fender a little will solve the problem (doesn't sound like it), you can get really good results with a pneumatic sanding disc. Otherwise, I had custom fenders built for mine for $400.
I don't know enough about your front headlight bracket, but that sounds like something that'd be easy to fix.