Both of the things you mentioned are in fact inherent problems with the '67 down design. A cantilevered beam design is an inherently weaker design, its engineering 101. That is not to say they can't be used or that they're dangerous, but in this case the '68+ version is a better design.
And sourcing the idler arm is a problem too. The '67 only version is expensive, and if the quality of the reproduction arms has dropped then the steering will suffer.
