Need help with brakes before I go nuts
 

On my 67- I have bled brakes twice around, and the brake pedal still goes to the floor with little resistance. I bled them long enough to get clean new fluid out of the valves. The brakes on all four wheels seem like they're dragging justa bit. you can still move the wheels, but you can hear the brake drag. I assume it is the MC, but only because I don't know what else to blame. Can anyone help? Thanks