Soft pedal on '62 Valiant V8 conversion

I'm using a dual-reservoir master cylinder; Kelsey-Hayes 4-piston discs on the front; 11" drums in the rear with a proportioning valve; and the brake lines are new. I'm not sure what pushrod I'm using, and I'm pretty sure I've got it bled well, but not completely sure. The pedal goes most of the way to the floor on the first stroke; then comes up to where it should be on the second stroke. Would anybody have any suggestions about what I should check? How can I check and set the pushrod-to-master clearance? Thanks.