I don't know your engine at all or how your bracket is attached to the block, but I had a similar problem once (I don't remember what car I was working on)- I took the whole braket off the engine - when I put it back I was able to put it on upside down. It looked OK and I was able to bolt the alternator on, however the the top adjuster bracket was about an inch off as was the alignment of the belt. It's a long shot but maybe the bracket it flipped.
