[Paul A]

On the 2nd ERA Cobra I built, I installed Tilton calipers. They made a kit for the inboard mount. They have all the components to ensure front/rear bias, etc.
Don't worry about the inboard feature, they mount in the rear position and I cut our a large window in the trunk and installed an aluminum cover with aircraft Dzus fasteners and used their hand tool for quick removal & attachment.

Keep in mind that the rear brakes are only doing about 30% of the stopping power, so heat buildup in club track days (10 lap session) will not be a major issue. The emergency calipers still remain in the front.

If you think heat buildup will be a major factor in longer lap sessions, you could install two electric fans (one for each rotor) just above the drive shaft tunnel to blow cooler air from the cockpit area into the critical heat zone.

Also, attached is business located in La Habra, Calif that makes compete Jag IRS suspensions using either a Ford 9 style 3rd member or a Quick change 3rd member. They have everything from flange face to flange face in several different widths. They are well know in the streetrod world with a great reputation. Some of the biggest car builders in LA, like Chip Foose, use Kugel rearend assemblies in their vehicles. kugelkomponents.com