My information came from documentation I had access to when I worked for the company that made Raybestos and United brake parts. We had researchers who would study the part numbers of all the car makers brake parts, and when a new part number was found, one of these parts was ordered through car dealer's parts department, and the part analyzed and documented by engineering for potential addition to our product line.
This process went on for decades, we had documentation going back into the 50's.
We kept the samples after they were analyzed. Unfortunately over the years before I began working there in 1990, there had been several housecleanings, and obsolete part numbers, parts we had discontinued from our line, they had tossed the samples. Rare samples like 2229171 and 2229191 were tossed a few years before I was hired.
In my spare time/boredom, I studied the Mopar master cylinder documentation for the late 60 through early 70s. I started buying up some parts I found for sale that had casting numbers I saw on documentation of interesting master cylinders that had been scrapped from our samples.
As far as the original question, I believe the casting number 3461176 is correct for 71-75 power disc A bodies.
As far as my info on 71 on A body manual disc my information is a bit incomplete unfortunately. There is a part number for a manual disc master cylinder used on B and E bodies. Maybe it was used on A bodies too?
Here is a picture of it, casting number 2229271