I had the same trouble after car sat for a long time, no amount of bleeding would get a decent pedal and adjustment wasnt bad. I even replaced the master cylinder. Someone here advised me to leave a brick on the brake pedal overnight and bleed the next day, that did it.

These old cars are hard to bleed - I have never heard of that, but it makes sense. A pedal that hardens up as you pump is always a fluid problem (as far as I know). As mentioned before - the other way of bleeding hard to bleed systems is to get a plastic lid from an old bottle that fits on the top of the master cylinder and modify it so that an air nozzle can be fitted and slowly push the fluid through the lines with compressed air.

But I will try the brick thing in future that is a good tip!