What master cylinder

I have a 72 cuda with front disc and 11” drum in rear. Had manual brakes. I cannot find a master cylinder listed for this application... any help would be great

According to the specifications in the 72 Plymouth FSM, which can be freely downloaded here, the master cylinder is the same for power or manual disc brakes.

Rockauto lists several choices.

On my 70 Challenger that originally came no power brake, drum brakes. Replaced drums with discs. Horrible brake action that required excessive pedal force to stop car.

Finally installed a very soft pad that helped,,,but ended with filthy wheels after very few miles of driving from brake dust.

After much investigation and complete BS from many “experts”, I learned that smaller MC bore increases braking pressure on discs than does larger bores. Sounds A*** backwards but is true. Found this cylinder, installed it,,,went to very clean ceramic pad, brakes are very good. Original drum brake MC was a larger bore.

Do not know if fits your Cuda,,,but you get the idea,,,,in this case smaller is really better

https://www.amazon.com/gp/product/B001PYO1PU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

On my 1970 Charger I'm using the 7/8 wheel cylinders and 15/16 master cylinder. The pedal feels good.

This has been addressed a number of times so definitely worth a search on the board, but yes the consensus is to use the 15/16 bore master cylinder, as shown in the link (or if you are not worried about looking stock-ish, an aluminum 15/16 based on the later model if anyone is still offering them). Note the original application for the iron one was mid-70's A-Bodies with POWER brakes, don't be put off by that, this is what you need for your manual discs on your Cuda. The 7/8" rear cylinders also a good idea, though you have 11" rear drums rather than 10", so not sure if this would affect that choice.....

surprisingly the 10 brake has more pad area than the 11 inch brake-----