I think that this kit would make a good 'generic' starting point for a MII 5-lug 8inch rear. But anyone that buys it should be prepared for a little machine work.
I want to keep my 4-lug axles (dare to be different!), so I need to hit the local pick-a-part and look for old Escort GT's, '80's T-Bird Turbo's, or newer Contour/Cougars. I believe that all had 4x4.25 lug patterns and had rear disc brakes available on some models.
If I gather enough parts and brackets I should be able to cobble together something. The main trouble will be to find a rotor that leaves room on the wheel side for the caliper, a mounting bracket that mates to the axle without excessive spacers, and calipers with provisions for emergency brake cables.