@gunrunnerjohn - thanks for the suggestion to look at Lionel (or Kline) knuckles - definitely worth a shot.
@PW53inVa - agree that a straight replacement from RMT would have been "easier" - just swap the trucks. If a Kline or Lionel knuckle works then replacing just the knuckle is easy without a need to remove the truck. Hopefully the rest of the truck does not disintegrate over time . I like the cars - getting them back in operation will be good.
Thanks!
- Luther