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

Gang of people with great taste:

Has anyone done this conversion to get rid of that iron lump or 4-bolt iron master cylinder (MC)? Specifically, have you used an aftermarket MC or reconditioned later model MC...and does the manual brake stock push rod fit the 2-bolt MC and adapter?

"Doctordiff" offers a conversion kit with retaining ring for $100 (+$13 shipping). However, from my studies a 1979+ non-front wheel drive MC is the same thing for a fraction of the cost that looks the same. I sound pretty cheap here now that I'm reading it.

I have searched these forums and this logical "mod" has not been covered! I mean the benefits and size of an aluminum MC is significant. Mine is pretty rusty on the inside which cannot be good for the brake fluid. What gives with the lack of coverage or is it so easy what am I whining about?

In the picture I had to secure the MC lid better because it was leaking...effective solution.