Brake bleeding ?

[boatpuller]

Installed my rear disc brakes this weekend, all new rubber lines,new front pads, rotors turned. Brakes had been getting kind of spongy in the last month or so, when I started bleeding the brakes couldn't get the pedal to stay up, it would go to floor, so went down and bought a brand new master cylinder(Raybestos) bled on bench, installed, rebled, starting with antilock valve then all wheel cylinders, pedal got hard, felt solid until I started engine, then pedal slowly goes to floor, even pumping it up doesn't help it goes to floor after a couple seconds.Have gravity bled, bled the old fashined way and vacuum bled. I even loosened brakeline at master cylinder with my better half(she might read this) holding pedal, if pedal was on floor would still get pressure out of MC on front port(for RR brakes) but wouldn't out of rear port. Could only get fluid out of rear port(for FT brakes)in the first amount of time after she pumped them up before it went to floor.
Here's my question, do you think that the fluid could be going by the piston for the front brakes(rear piston/reservoir) only when I have the extra assist from the booster?? If not do you have any other ideas, one other thing, when you push on the pedal with the reservoir cap off the front reservoir spits up at you but the rear one just barely moves. I'm going to see about getting another new MC, just wondering if there isn't something else I should look at also? On my dirt driveway the rear wheels will lock up but the fronts don't. Also put vacuum gauge on booster and the pump is putting out plenty of vacuum.
Thanks for any suggestions,
Caleb