The bracket in my photobucket link is on a 1972 250ci block. I ran the numbers on the stamp. I have another 250ci next to it in my shop. They look the same. Neither have the boss for the lower 2 bracket holes.
I have a freshly rebuilt 1964 230ci in my 1965 Chevy AND IT DOES HAVE THE BOSS WITH THE 2 CORRECT HOLES!
Well it's good to know that what I bought is really an AC bracket.
There is a listing on eBay for AC brackets for these inline 6 cylinders. LINK HERE. ANOTHER SELLER.