I had a T bird rack on a MII I installed a few years back. the mounts didn't look like that but rather were flush on the front and rear sides.
here is a link to summit's site with a few options. I wonder if yours was a one-off year or something. you could swap them out to the more standard ones if you desire, it adds to the price of the rack but that way you get the ones you want/need. note that some will offset the rack to be higher or lower than the stock location.
https://www.summitracing.com/search/...el/thunderbird