I didn't stop, there's no concept of shear where a '67 idler mount is in double shear. The stud is in single shear at the mount, because that's all it can be with a single plate mount.
So, it's a cantilever mount that puts the idler stud in single shear.
Now, is it dangerous? No. But it's an inherently weaker design than the double shear mount that replaced it in '68 and going forward. For a cruiser with narrow tires and low annual mileage, whatever. Spend a grip on a single idler that will probably last the next 30 years. For a car set up with wider, stickier tires and driven frequently? Nah, replace the K for one with the improved idler mount. For a handling set up don't even mess with '68-72, go with '73+ for the better sway bar mounting and routing.
As far as adding a '68+ style mount, anyone that can take some accurate measurements and weld can do it without too much difficulty. Members here have built a jig to locate one, it's not all that hard. It certainly doesn't have to be a "disaster" if you understand basic geometry and can weld as well as the factory did, which is a really low bar.
