I'd say lose all of the low end Simplex crap if you want to give your Dad a reliable bike, but no Suntour rear derailer will fit that Simplex hanger.
The Simplex derailers and shifters are old and brittle and prone to breaking at the worst possible time. My Criterium broke when I was 5 miles from home and it was only about 10 years old.
Rootboy has the solution.
Last edited by Grand Bois; 02-09-12 at 07:09 PM.