Rear Disc Brake Conversion

I have upgraded all the front already to 73 spindles and tubular uppers. I just having issues with the rear brakes and want to switch to Disc. I heard about the explorer rear brakes but the ones Cass sells are all new parts and Just a phone call away. I was wanting to hear all the pro's and cons of the different disc brakes that are out there.

Do you run the 11.75 front rotors? That is much more of a performance upgrade than rear disks. That should be done first or at the same time.