I have a 72 b-body with the power disc brakes. I may be crazy but I want to get rid of the power brakes and go manual. anyone ever done this? do I just need to remove the booster and install a manual master cylinder?

My 70 Charger had 4 wheel drums when I got it. I added a 1975 Dart power booster & MC and the 11" front discs. Everything was a bolt in deal. Many years later I decided to switch to a manual MC. I had a few things wrong and because of that, the brakes felt terrible. Hard pedal with minimal brake force. I wimped out and put all the power related stuff back on.
Now, 4 years later, I am ready to try again.

If you have rear drums, this should be easy to do. I'd go no larger than 15/16" on the master cylinder though. The bigger the bore, the harder the pedal in many cases.

My e-body needed a new pushrod, master and the firewall reinforcement plate. As mentioned, 15/16" should be about the max. Wilwood suggested I run a 7/8" with the 4-wheel disc setup I am buying.

Manual disc brakes will work okay if you have the larger 11.75 rotors. I have 13 inch rotors on my B body and the manual disc brakes are just about perfect. It is all about leverage and friction. One problem with the factory brakes is that it is harder to find different pads. If you switch over to an aftermarket caliper then you can find lots of different pad compounds. Something soft and grippy will help with the pedal feel.

Ok sounds simple enough. Now with the reinforcement plate, I take it there is a different from power booster to manual?

Manual seems to have less initial bite but are way more manageable and pretty hard to get to lockup. All bonuses IMO. People sometimes feel if they don't lockup easy they don't work.

Ebody does, the factory one for a manual is shown here. I'm getting a new one laser cut on Monday that looks a little better.

I have driven manual disc Darts and Dusters for several years. Their braking abilities have always impressed me. Sure, you can get the wheels to lock. I never had a problem with the rears locking like I have read in magazines though. It was because of the great linear feel of the A body cars that I made the switch to a manual MC in 2012. I was really disappointed with the performance in the Charger though. I wrote that I had made several mistakes that collectively contributed to the outcome.
I tried 4 different master cylinders that all gave the same results: Hard pedal with poor results. My setup felt like a power brake car with zero vacuum to the booster. The smallest MC I used felt the best but it was still nowhere as good as the Duster/Dart setup using the same size MC.I put the power setup back on and added a vacuum pump.
Later, I was looking to improve even the power setup. I found some Carbon-Metallic front pads on RockAuto. I switched to 2.75 piston front calipers up from 2.6. I swapped in a brake pedal that I had modified for better pedal ratio. Then.....It did not occur to me that the disc/drum proportioning valve I had in there could be adding to the problem. I swapped in a drum distribution block and the brakes are fantastic.
I still want to try the manual setup again. I bought another 15/16" MC, the 4 to 2 bolt adapter and an adjustable brake pushrod from Dr Diff.