That part is referred to as a cowl shoulder. Look at the pic and you will see it comes as two pieces. You cut the outer cowl off, then the inner portion in the blower motor and kick panel/door hinge area. Afterwards you weld the outer skin on. This is listed as a chevelle part, but surely all a-bodies would work.
http://cgi.ebay.com/ebaymotors/68-19...Q5fAccessories