I'm doing a swap on my 72 challenger. The car has power disc brakes up front. I've decided to switch to manual brakes for my hemi swap. I have a new aluminum 2 bolt master cylinder with the rod. My question is, what else do I need? Do I need a stiffening plate? Or master cylinder adapter? Or both? I'm confused...?

Not sure what may be needed as far as a firewall adapter but make sure when doing the switch you use the correct proportioning valve/distribution block.

I used the two bolt m/c and the 4 to 2 bolt adapter that Dr Diff sells. Make sure you also get a manual push rod.

You need a firewall plate that comes from a manual brake car. The boosted firewall plates have the wrong stud spacing. You need to make sure the piston in the master cylinder is no larger than 15/16" or the brakes will be crap. Also, make sure you have a 6-1 pedal ratio or the brakes will be crap. That may involve drilling a different hole in the brake pedal. Remember - Changing the MC piston diameter is directly related to the pedal travel for the same fluid pressure. You must make sure you have the extra available travel in the pedal using an adjustable push rod. I set pedal travel by making sure the MC piston bottoms before the pedal is at maximum travel. I bleed the MC on the car after setting the pedal travel using looping fluid lines back into the fluid wells.