Seems to be a typo in the FIAT shop manual. It's actually M12 x1.25 (extra fine instead of fine). In fact, the same page shows the correct spec for the nut, but not the bolts. I bought a pair of M12 x1.5 bolts, and my brother Carl sawed off the heads for me. Later I tried them out and they stopped after about 1 or 2 mm. I thought to myself, "Wrong pitch?" Sure enough, when I dug out the car's own bolts and nuts from their ziplock bag they also did not work with the new sawed-off bolts. This time I took the car bolt and nut with me to the hardware store and tested them with the new bolts. M12 x1.25 it was. This was the first time I lost a tiny bit of money by relying on the info on XWeb. Not a big deal, because we can all blame the shop manual, and I've gained tons of valuable, free information from here!
NOTE for Kurt and Dan: If it's not too much trouble, please edit your posts above to include the correct size, something like "[NOTE: typo found in shop manual. It's actually M12 x 1.25]" That would help slow down the spread of misinformation here. If you do that I'll remove this note at the end of my post.