A body K member

IMO, the actual design of the early idler isn't as good as the later one. It's just a matter of physics, leverage, and the actual idler arm materials used. Now, when it comes to the metal thickness and alloy involved, plus the quality of the welding.......that might be a different story. The later design is better, but, the actual strength might not be. For the street, it's mostly a non-issue except for cost.