Which aluminum master cyl for 71 Duster

I searched the posts here and found mixed answers. I want to put one on with the 15/16 bore. I have a non power system with Kelsey Hayes up front. Some posts have said to use the Raybestos MC 39638, available for about $50. Others have said to use the Dr. Diff unit because he mods them to work, at $100. So my question is for anyone who has the Raybestos unit bolted to their car and can say that it actually works like it should. Thanks.