Since we used to run camel back heads without accessory holes we had to get creative on making brackets so they didn`t break. One side mounted to the header, the other to the water pump, we made a piece of curved metal that went from the water pump to the upper most bolt hole in the PS bracket.
The bracket on Ebay is used for 69 and later pumps which uses the head as a mounting point. pre 1969 used the brackets without head accessory holes.
In the cases where we didn`t have time to make a custom piece, all I did was use a bolt with a shouldered head, and a large flat washer to assure all the clamping force as possible was placed on the pump and that always worked as well. I would also used shouldered bolts on the exhaust mounting side.