Good idea as the block will also keep the piston to far and possibly scoring the rubber pieces.

Another thing to remember--as the brake pedal hits the floor, the fore and aft motion of the master cylinder piston becomes an up and down movement possibly allowing air into the MC.  Put a piece of 4x4 on the floor next to the pedal for a stop, as u bleed the system.  One of my service manuals mentions this.

the shoes need to be in contact along both surfaces agains tthe drum.  If the adjusters are nto correct, and the shoes only contact partially, you can not get a good bleed.  Aslo if you have insufficienet pedal free ply, movemet of the pedal and linkage before the MC piston begins to move, you also can not get a good bleed. 

This is a P10 and only has one wheel cycliner per wheel. I can feel the shoes make
contact with the drum, however, there is no real resistance on the foot peddle. The MC is new.

The hydraulic system will not start to build pressure until all drum cylinders have reached the point where the brake pads are against the drums.  If your car is similar to my 48P15 then you have 6 wheel cylinders.  Any combination of these cylinders and brake pads being out of adjustment will create your problem.  The master cylinder can not push enough fluid to engage the brakes.  The next possibility is a Master cylinder rebuild if all the wheel cylinders and pads are adjusted properly.  If the car had good brakes when parked and then all of a sudden not, I would suspect the Master cylinder.

The link Greg posted is a good place to start. 

Good Luck, Chet?

While not the exact system the adjustment process is the same.  Read this and you will have a better idea of why adjustment is critical on these systems.

http://www40.addr.com/~merc583/mopar/framesets/wipbrakeframeset.html

In addition to Bob's questions/comments, how are your brake shoes adjusted? Seems like the brakes are a lot easier to bleed it the shoes don't have to move a lot to touch the drums.

When you bled the brakes did you start from the farthest point from the master cylinder, meaning the passenger side rear wheel?

Then go to the driver's side rear to the passenger side front then finally the front driver's side wheel.

You MUST make sure that all air is out of the system.

Also the plunger in the master cylinder may not be seating correctly.

Are all your wheel cylinders in good shape and not seeping?

Hope this helps,
Bob

My 1940 plymouth has absolutley no brakes. The master cylinder is full, the brakes
were bleed, I hope well enough. However, there is not even enough pressure to
have the brake lights come on. Where should I look for the problem?