69 Dodge Charger trouble with braking

[1969boxercharger]

1969 Dodge Charger with disk in front ,drums in back. i have bled the brakes and master cylinder to the best of my ability. my issue is this...if im going slow or cruising speed the brakes seem to work fine. if i speed up i have to pump the brakes a couple of times to stop the car and i foot goes all the way to floor. also notice when i back up or do a u turn,the brakes get very soft and need to pump...please help.

[lukedukem]

Are they power or manual brakes. if power, it might be booster issue


Luke

[68 RT]

Needs bled, or rear shoes not adjusted right.

[John_Kunkel]

Master cylinder is bypassing internally.