I have a guide somewhere as to what calipers are what as there are three you may come across(26mm, 30mm and 30mm iron), but i'm moving so I'll dig it out when my pc is up and going again.
Best option is the 4 pot 30mm calipers and 280x30mm rotors to suit. You can get then from dba as blanks so you can just drill them to 4 stud. You need the outside diameter of the rotor machined to 274mm. Once this is done the caliper and rotor will bolt on.
Wheel clearance is an issue. It's more the space between the caliper front and where the spokes of the wheel meet the centre that doesn't clear. 2 options spend money on wheels designed to clear big brake upgrades (what I did) or 2nd option is spacers, which I hated the idea of.
The last thing you need to do is get new front lines made up from the hardline behind the strut to the caliper. You can use the stock line but 9/10 the banjo won't fit properly and I don't like the idea of spacing it out with washers. After all it's what stops your car so do it right the first time I rekon.
I'm pretty sure that covers all of it. If you have any more questions just ask.