I've read about seating the pads and shoes by getting up some speed and then jamming the break pedal hard to get them seated. Might help.
Another thought, I once put new discs & pads on and forgot to clean the oil off the discs first with brake cleaner. Those suckers wouldn't stop on a 20 dollar bill, let alone a dime. I cleaned the discs and put new pads on and it stopped on that dime and gave 9 cents change.
It was on my '78 D-100.