Concur. I think the base is relative to Nova and Chevy II vehicles only for '62 model year, and perhaps '63. The 'T' cross section type of mast for the jack was something I thought was '62 only. Schwabie has a lot of experience with these and seen quite a few jacks, bases and hooks through the years. Some are marked with year and model, others have no marking. I have seen '63 vehicles only with the 'trapezoid' cross section type of jack post, and that type of jack post through '67. The jack hook part that attaches to the cranking mechanism varies a lot in those years.
Not near my car today, but will be next week. Be good to post a thread about jacks from members having a definitive answer for the type of jack kit used in each year.