i had a 76 chevy that had a lot of bondo on it. when i bought it you could not tell, but over the years that i owned it the bondo cracked and shrank, it ended up looking pretty bad. i got a wild hair one day and started sanding the bed down to repair the old bondo and repaint it. what i found was a bed that had been almost rebuilt with bondo. needless to say i was worried, so i sanded it up nice and primered it. i sold the truck a few weeks later. it was not worth the hassle to of fixing. i told the guy who bought it what was going on and even discounted my price. i felt bad not telling him what was up with it, darn conscience anyway. i have never had a good experience with bondo. as a body smoother / filler it is top notch, but as a tool of major repair i am skeptical. it made me sad that the PO had done that instead of doing the repairs right. if i were you i would sand it down and make it look good, paint it and forget it. when you have the money to do more i would pull the fender and get new ones. but until then bondo is really cheap. good luck.
