I've just finished a conversion to front discs, with a dual master cylinder upgrade. Replaced all the brake lines and flex hoses, and replaced the huck rear wheel cylinders.
You want to make sure that you bench bleed the master cylinder, as an air pocket there can cause problems bleeding the system. Take a little time and adjust the wheel cylinders to get the brake shoes dialled-in.
I found it took a lot longer to get fluid to the rears than it did to the fronts, so patience will help as well. Make sure you've got the brake pedal travel sorted out at the master cylinder, so that you're moving enough fluid with each stroke.
