Incorrectly torqued spindle nut will sometimes cause pulling, as well as worn front end parts. Also front end alignment problems and incorrect tire pressure can cause pulling. Mismatched brake drum diameters, rather if one drum is new, and its sister on the same axel has been turned, this can cause pulling. Also any contaminants on brake shoes or drum will cause pulling.
Defective flexible brake lines can cause pulling by delivering unequal fluid pressure to wheel cylinders, and problems allowing fluid returning freely to master cylinder once pedal is released.
Flexible brake lines should be replaced if dry & stiff, cracked, chafed, pulled from fitting, or over ten years old. If you don’t see a date stamped or printed on a flexible brake hose its replacement time is way past due. Change out all three, they are relatively inexpensive, and a big safety concern.
Where you were experiencing pulling before brake work, I suspect bad flexible lines, front end parts, and or alignment problems.
If you have a single pot master cylinder, you will need to bleed out all four wheel cylinders starting with most distant from master cylinder and bleeding to closest. That is starting with: left rear; right rear; right front; and lastly left front.
If you have converted to a duel pot 67 and newer master cylinder, you can bleed a single axel without disturbing the other half of the system.
Pulling brakes need to be corrected ASAP. One can deal with a pull under gentle dry braking conditions. Under wet conditions if hard stopping is attempted the car will most likely become uncontrollable shooting you into oncoming traffic, or out into the pucker brush, same for full lock-up on dry pavement.
