Rear Brake Problems

hello folks, i got a problem with rear brakes on my 04 mach one. i replaced the rear rubber brake lines, calipers, rotors, and pads. now i dont have any brake pedal. i have bled the brakes numerous times, didnt help. the emergency brake can be pulled up 5 clicks though. i dont see any leaks anywhere. i have been told it could be a master cylinder, but i'm unsure of that. i'm not really sure where to begin diagnosing the problem at. any help is appreciated.

both bleeder screws are on top of the calipers. the reason i mentioned the emergency brake is because at the beginning, it didnt grab at all because the calipers hadnt tightened up. they have now, but theres still no brake pedal there. when we bled the brakes i also did the front. one curious thing that happened is we noticed when bleeding the front, when the bleeder valve was opened, the pedal would goto the floor. they havent done that on the back. fluid does come out the back but the pedal doesnt go down. we've been bleeding them the old way. the brakes were rock solid before we did all this, but the reason we did it is because this car is really eaten up with rust. the rear rotors had massive rust spots, not surface rust but actual deep pockets of rust. the caliper had rusted so bad they were peeling off in layers.