As pictured in 1964 body manual these are actually factory installed. Single exhaust received one on pass side inner fender at base of inner fender Dual exhaust received both sides. They are heat sheilds due to high temps just ahead of resonators. they were to assist front brakes in keeping temps down, factory records indicate this model as with others experienced high levels/ brake fade. The manual shows these sheilds as being held in place by two/three bolts. these sheilds are groved and run straight down from the inner fender toward the road. I got this info from a gent who's dad worked on the line at flint and purchased a cat new in 64. He has since passed, but his son owns the cat. silver / blk vinyl top, interior 425 dual quad. {super cat ] thanks to all who responded.