There is a direct mechanical link between the pedal and the master cylinder. If the pedal is stuck to the floor, the master is also stuck down. When you said "bleed the system" I assume you were talking about the power steering system and that your brake fluid wasn't messed with and is still solid. If that is the case. You might have what happened to me last week. I was fitting a hydroboost to my M715 which has a 1976 Corvette non power brake master cylinder. I couldn't bleed the brakes by pedal. No air with vacuum or pressure bleeding, but no pedal resistance. Just to the floor and all 4 tires spinning. I was calling the parts store for a replacement for the junk master cylinder they had sold me the day before and saying bad things about Gimpy who gave me the hydroboost 6 years ago. Turns out the push rod on the master side of the hydroboost was too skinny and was sliding 3 inches into the master bore where the non power push rod was supposed to fit. My master wasn't getting moved while I was pushing away like crazy on the pedal. I made a spacer to stick in the bore and have amazing brakes now.
Since it is so easy. Unbolt the two master cylinder mount bolts and slide the master away from the hydroboost some. See if the diameter of the hydroboost push rod is the same as the one you took off. Also, have somebody push the pedal slowly and make sure the push rod is moving. If it isn't, you got a bad one. If it is, then your master could be bad or you could have what I had.
Sorry for rambling around some, but I wanted to back up my reasons.
