Rebleed Master Cylinder?

I changed from a single reservoir to a dual reservoir master cylinder on my '66. It's power disc, rear drum. Master was bench bled on a vise, then installed. After all plumbed in, during bleeding the system, the large reservoir went dry, probably sucked some air. I've bled the system with a quart of fluid, but the pedal goes almost to the floor, and the car barely stops.

Should I rebleed the master cylinder? Any other ideas?