Bruce,
By "dust covers", do you mean the little rubber parts that move in and out with the pistons and keep the dust off (out of) the pistons? Or, do you mean a cover that keeps brake dust from getting on the wheels?
On my 230SL, I replace all the rubber seals on my Girling 3-piston calipers. There are ones that go around the inside of the cylinder and the others that I described above. It's a PITA, but any calm and patient person can do it.
Rodd
1966 230SL Euro
1994 E420