I'm not 100% sure about 66/67 Chevelles but I believe the one in your pic was never used on Chevelles. The correct Chevelle reservoir has a different bracket welded to it. The correct bracket has 2 bolts. One goes to the fender, and the other goes to the fender to rad support bolt.
Here's a shot of my 68. I believe this it is the same set-up as 66/67.
