No they don't have to be. I got myself a set of G35/Z33 front Brembos and will going down the route of using time serts.I recently sold my Fairlady Z33 real calipers and brackets for them to fit a GTR (and other Nissans) using 370z rear discs, geezer on eBay doesn't appear to have any of the brackets listed anymore either. Upside 370 rear discs are cheaper, downside is you end up with bigger discs at the rear than front!
Must they be R32 / R33 Brembos calipers For the front?
I ask because I fitted Z33 Fairlady / 350z calipers, new piston seals and dust boots, c hook discs and brembo pads for cheaper than it would be to have bought 33 GTR calipers alone, and I didn't drill the hubs either, used 4 wurth timeserts (2 for each caliper) which reduced the m14 bolt hole to m12
Size - M12 x 1.5. Length - 24mm. QUANTITY - 5 x INSERTS. Its thin cross-sectional area allows for installation in areas of limited space and clearance material. PA20 to 38, PA41 to 49, PA60 to 78. KA27 &28 KW1 to 17.www.ebay.co.uk
Set of 350z Brembos can be had for between 3-400 quid, and not 800+ for one's from a 32 or 33 probably just a front set.