Chevelle Brake Problem

[Damien]

I have just replaced my booster prop valve, master cylinder and the lines from the distribution block located on the chassis rail to the master on my 70 SS Chevelle. The booster and prop valve are restored items from Brake Boosters and the master cylinder is repro single bail 70 style with bleeders that came from Ground Up. The booster came with both long and short pins for the master and I installed it with the long pin as the master has the deep hole in it rather than the indentation that is for the short pin. So I change everything over, bleed the brakes, and the pedal just about hits the floor before they barely engage. Ok, do some searches, perhaps the rod out of the back of the booster to the pedal is a fraction long in adjustment and is hanging the master open? Adjust that, seems ok, gravity feed the brakes as I'm home alone, still the same! Now I'm getting fluid to all 4 corners, no problem. There should be no need for shoe adjustment, wheel cylinder replacement, any of that, doesn't leak and as 2 days ago everything worked great with the old set up. Obviously it's something I have or haven't done. Any help is greatly appreciated.
Thanks!