do you have the calipers on the correct side.a friend of mine,(no,not me,really),had them on the wrong sides,& couldn't get a poor pedal.the bleed nipples should be at the top of the caliper,so the air can't get trapped in the
piston.if this is correct,try bleeding the master
cylinder.the best way i've found to do this is
run the bleed line back into the reservoir,so you don't drain the reservoir & cause extra work.if
this fails,pull the hand brake on,if the pedal
gets better,bleed the rear brakes.if all this fails,
then look at the m/cylinder.