try to find a BRAVO HGT in a scrapyard, and get the calipers off it. if the disks are decent, then take those too. you'd be as well to put new brake pipes on though, which you can get from fiat, and you'll need a new handbrake cable. i think they will stop you slightly quicker, but rear disk conversions are more for the look than performance.
Buzz (formerly LightWarrior)
The champion of the Bravo 1.4