I don't believe there were multiple styles of jacks. Every 68 jack I've seen has been the triangular style (not the square) like stovebolt's, Ed's, and jack #2. Not to say there couldn't be different versions, but I've never seen them.
There were multiple suppliers of the base, so there's many versions of that. But I'm not convinced the jack had multiple suppliers and, if there were, they would all be the same style (i.e. triangular) to fit the base.
Btw, there is a larger triangle post size that was used for big cars. The base is way too big to fit a Camaro/Nova jack.