Are they the same Brembo's as fitted to the GTV 3.0 V6 and the early 156/147 GTA, that take the 305mm discs?
If so, you would need to get the hubs from a GTA, and press them in with new wheel bearings. Not a straight swap I'm afraid, and you would need 17"s..
This might be of interest to you:
http://www.alfaowner.com/Forum/tunin...mm-330mm.html? (Brake conversion 284mm -> 330mm)
http://www.alfaowner.com/Forum/tunin...6-147-gt.html? (Group buy - big brake upgrade for 156/147/GT)