Getting back non topic (just for a moment ) s4/5 RX7 four pot calipers might fit the bill Brock. the sve's run a 290mm X (I think) 22mm disc. So it wouldn't be too big of a stretch to make them work with those discs. When I've been playing around with discs and calipers I've found that the arc on the top of the brake pad is tailored to match up with the arc of the OD of the disc it's been mated to. So you could need to space it down just a fraction more than you otherwise might to ensure that you have a minimum boarder of non contact patch around the periphery of the rotor. Although the effect I'm trying to describe is of greater consequence when fitting a caliper (and pad) from an application with a larger disc, onto a rotor with a smaller OD.
I would expect that running the pad from a 280mm application on a 290mm disc would merely mean that the non contact area or "lip" would be fractionaly greater at each end of the pad. Although as it'd be less at the center of the pad, you probably wouldn't even notice it as the rotor wore.
They don't call me the man with the rubber arm for nothing you know.............
Just checked the DBA website Bart and the s4/5 sevs run a 276mm OD disc but still 22mm thick, so much smaller than you thought. Im using mine on a 280mm disc so shouldnt have too many issues.
Sorry guys no real update - researching time thou.
I need to borrow off someone local if possible a standard B110/210/310 lower arm, strut etc with ball joint/steering arm attached and with top hat etc for measurements.
ill need to bolt it into the car etc for a week or so.
I'm getting stuck into the front suspension but want to retain lower arms and or make some the right length if i can due to track width and ease of lining up other parts such as radius (castor) rods etc.
Any help much appreciated and this work with hopefully help others in the future.
) s4/5 RX7 four pot calipers might fit the bill Brock. the sve's run a 290mm X (I think) 22mm disc. So it wouldn't be too big of a stretch to make them work with those discs. When I've been playing around with discs and calipers I've found that the arc on the top of the brake pad is tailored to match up with the arc of the OD of the disc it's been mated to. So you could need to space it down just a fraction more than you otherwise might to ensure that you have a minimum boarder of non contact patch around the periphery of the rotor. Although the effect I'm trying to describe is of greater consequence when fitting a caliper (and pad) from an application with a larger disc, onto a rotor with a smaller OD. 
