[Dan Case]

Originally Posted by krausewich

I assume one side of the bolt head is ground or milled down to fit into the notched portion of the AArm spacer sleeve end?
This was done to make the assy. tool free on one end?

One side of the head is milled flat down to the diameter of the shank. On end the pin heads look D shaped. AC Cars did similarly with spring eye bolts. In each application a corresponding pocket is machined to mate with the flats. The mating pocket in control arm mounts is large and robust. The mating feature in front spring trunions is pretty robust. The weakest application is the rear upright which has a very small, in comparison, locking feature. The rear lock features are normally so small and shallow that the use of a high powered impact tool to install nuts can spin the pins and shear the lock features completely off the rear uprights.