You don't want to fit them over the bolt and spire bolt on the disk. Rather you want spacers with 6, rather than 4 holes. The extra small holes are for the nut and bolt.
Alfa 155s have -- IIRC -- 8mm front spacers (and longer spire nuts to suit). You can pick them up for pennies from a scrapper (Alfa scrappers tend to be specialists, but you'll find some in generic scrap yards) these fit straight on. Or, try your FIAT dealer, as I think Aaron mentioned them doing 10mm spacers at a sensible price.
Failing that, get a hubcentric 10mm spacer from tweeks or somewhere with 98pcd, bolt a disk to it and use the disk as a pattern to drill the clearance holes for the bolt & spire bolt in the spacer.