I have a set of a-arms in a parts lot that look home made & they have the same bearing end your gibsons have. They used a c-clip on them & they were tack welded in because it looks like they were trying to push out. It makes me think Gibson uses the spherical retaining ring to prevent them from pushing out & being a full 360 degree clip instead of having an open end like a c-clip it seems like they would be stronger as well. Just my .02