Can I see your pics of 69 B body master cylinder mounting?
Mines has 4 studs through ms with nuts on the inside. Seems backwards to me?
Manual drum brakes please? Thanks, Don

Do you have the adapter plate for manual brakes? The studs go through so you can get to the inside while it sits still and put the nuts on.

Manual brakes has studs on the master cly and power has the studs on the booster. Just carefully drive the studs out and secure them to the new master cly if you are going back with manual brakes.

What the OP has is correct. Since the m/c he has has four studs it is a cast iron stock style. Now he needs the correct m/c backing plate for manual brakes - it will have a round hole instead of the wierd-shaped one.

Those studs are what help secure the pedals to the firewal - so they are necessary. While it is "uncomfotable" to install, its not a big deal. The studs are accessible inside the car to install the nuts.

There is no adapter required for this unit - only needed for the late model aluminum 2-bolt m/c's

From what you said I think I do have the adapter plate. Here's a picture

Thanks everyone for your help. Too bad the factory didn't put the studs on the inside. As I get older I need more room to work under the dash so I took the seat out. I was worried the brake pedal bracket would fall down.
I have a 69 Dodge service manual and it says take off 4 nuts and plunger bolt easy as pie.
Thanks, Don

Yup, that's it.

I regard that plate as more of a reinforcement, but no matter.
It should be a fairly glossy black.

Agree on under-dash work: probably my least favorite.