11"x2"? That's what the front of my B-body has. The 11" rears I have are all 3". That's the Dip, the Ramcharger, and the Sport...
As for the conversion Pop and I've done the 11" brake upgrade on the Dip using the backing plates from an 11" car. From there it was just a matter of ordering shoes, hardware, drums, etc, for the cop car. Seems to me that if you have the backing plates you could order up the drums for a 11" brake B-body.