I make brackets that mate first generation Viper calipers and 11.75" C-body rotors to B/E/'73-A body drum knuckles. See below:

http://www.doctordiff.com/viper-caliper-mounting-brackets-for-mopar-drum-knuckles.html

I also reproduce the AR000 Wilwood on 11.75" caliper brackets. I haven't made a listing for this part yet, but I have plenty in stock.

http://arengineering.com/wordpress/wp-content/uploads/000.pdf