Brake pushrod length.... and other brake woes

I'm going with a problem in the rear, and it's probably those new shoes that are only contacting at one place ; they are gonna have to break in . Or you can get them cut to match your drums.
Over-travel of the pedal is almost always due to a situation in the rear. And that is by design. In the past I have clamped the rear flexline on my car to prove it, but that is a bad idea with an old line, as occasionally it damages the line inside.
A better idea as offered by Inertia, is applying the parking brake. But the best test I have done is to clamp the wheel-cylinders pistons in such a way that they cannot advance out of their bores. This will prevent any fluid from leaving the M/C and the pedal will immediately get high and hard......... if there is no air in the hydraulics. PITA test but it tells the truth.
And BigBlock is bang on with the pushrod advice.
The clamped wheel cylinders will also point out a too-short pushrod. But you have to be careful to not make the pushrod too long. This will prevent the fluid from returning to the reservoirs thru the compensating ports. When this happens, the pedal gets lower and lower over time as the friction materials wear off. But worse is that in some situations with disc brakes, as the fluid heats up it expands and if it cannot get back into the reservoir it forces the pistons out,dragging your pads on the rotors,and eventually locking your front brakes on.
It is easy to see the compensating ports in action, but it is a bit tricky to not get brake-fluid all over the engine compartment. Here is the method I use. First as a newbe,cover everything within a 2ft radius of the M/C with cloth rags, lots and lots and lots of rags, and your entire fender, and down the firewall.
Then get a helper. Have him pump the pedal in rapid succession about 3 times and on the last pump, do not let the pedal return to the parked position. Just keep it about an inch from the top. Next, you go loosen the M/C lid, lift it up just enough to see the fluid,then have the helper slooooowly allow the pedal to return. As soon as the compensating port becomes exposed, you will see a little fountain in the reservoir. If there is air in the system, you could have a HUGE gusher of a fountain as the rear return springs ram the fluid back home.This is the reason for the rags, to prevent damage to your paint. Of course you should have a back-up plan for this, so you can signal your helper to stop lifting and instead start pushing. This will close the port and stop the gusher. Then you secure the lid. Then the helper can relax.
The gusher does not automatically indicate air in the system. The same will happen if the rear brakes are out of adjustment. The three pumps in rapid succession I mentioned will push the rear shoes out, and the fluid cannot return fast enough between pumps, so every pump pushes them out a little further.... stretching the return springs and creating a pressurized hydraulic cylinder. When the pedal is released, the return springs send all the fluid back, and Shazzam you see the gusher.
Air in the system does the same as it becomes an air spring.
This test proves the C-ports are open and the pushrod adjustment is not too long.
I like to make the pushrod as long as possible to initiate braking action right away....... with the above caveat; too long is bad.
Oh yeah, in a good working system, one pump will,upon release, either just roil the fluid, or at most you might have a little fountain about an inch high, probably less.