4-bolt to 2-bolt Master Cylinder conversion on 71 Demon/Dart

Look here- http://www.forabodiesonly.com/mopar/showthread.php?t=279568

Besides a really nice piece at a great price, you can buy from a fellow member.
Also, I believe in the thread there is a response to your same question regarding the push rod. I believe the answer was yes it will still work.

Here is what I did in my '69 Dart using the adapter made by member hemidart67.
The black bracket for the valve is separate and sold by Wilwood.