stock Mazda alt had a 15mm shaft, so I ordered one of the dual pulleys from Racing Beat.  Since I had the alt off, I decided to install the new pulley, but after much effort to get the old one off, I found the new one won't work, so I'm back to my single belt pulley again.  The hole was the right size, but the rear side of the pulley needs to be flat, and the Racing Beat pulley is dished on the rear side. ----------------------------------------------

Yep, been down that same path Rusty and I still only have one pulley. I was able to squeeze a 2nd belt that only runs between water pump and engine pulley so that I have some possibility of keeping the pump going if I lose the alternator belt. If you want the belt number I'll get for you tomorrow.

Bernie