Well, if a new cylinder corrected the problem for a year or so, I'd simply purchase a better new ignition assembly and use it. It isn't a bit complicated. As you probably know there's a housing held in place with 2 screws. In most there is a small light (connected to the dash light circuit). Remove that housing, swap the new switch for the old and wire as needed. I wouldn't spend any time trying to repair the old switch. Like other things they do wear out and it sounds like the replacements are junk. Good luck.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
