The earlier Chevelles are great cars, but have one major design flaw-an ugly firewall. Not only do they have a seam that runs right across the middle, there are so many tack welds the thing looks like it has a bad case of acne. Having this as a backdrop to a highly-detailed motor is just a distraction. If you just want to smooth out the spot welds and eliminate the seam, then a few skim coats of body filler and some block sanding will do the trick.