Early 80's 200, 300, and 400 series Mercedes for the steering arms. 82-84 would be the best candidate. Make sure both arms are off the same car, they had 3 different arms that I have found over the years.
The hole at the thicker part of the arm is the hole that has enough meat to elongate towards the other hole. You can simply oversize the hole to 9/16 and it should be sufficient. You will have to shorten the tierod assembly by 5" and the draglink by 2 1/2". Whenever I've done this, I've tried to utilize the adjuster side and tube from a stock tierod when redoing the draglink. That way you have an adjustable draglink with a replaceable end at the pitman arm.