Air in the system is about the only thing I could figure. I did bench bleed the new master cylinder before I installed it. I had the rears adjusted pretty tight, just a couple clicks back on the adjuster before the drum was able to slide on. But I will double check that tomorrow. I will also try bleeding the system some more and see if it changes at all.
I do have minimal brakes but the only time the pedal really gets solid is when it hits the floor, lol. And yes you are correct, thankfully no ABS to deal with.