No idea, you'llbe lucky to find the right car in a scarppy as there arn't many 2.6L GSi about.
Could always buy new from VX dealer
You only need the pair of brackets and the 5-stud discs.
Or get them a bit cheaper through www.autovaux.co.uk
The 308mm discs and calliper brakets are available from VX they were fitted on the Vectra GSI, and if your converting to 5stud hubs, then no probs fitting
If keeping 4 stud hubs,ring Auto-Vaux. They'll sort you out.